Fix compiler and IDE warnings for .NET 6

lib/TweetLib.Browser.CEF/Data/ContextMenuActionRegistry.cs

@@ -2,7 +2,7 @@ using System;
 using System.Collections.Generic;
 
 namespace TweetLib.Browser.CEF.Data {
-	abstract class ContextMenuActionRegistry<T> {
+	abstract class ContextMenuActionRegistry<T> where T : notnull {
 		private readonly Dictionary<T, Action> actions = new ();
 
 		protected abstract T NextId(int n);

lib/TweetLib.Browser.CEF/Data/ResourceHandlerRegistry.cs

@@ -21,7 +21,7 @@ namespace TweetLib.Browser.CEF.Data {
 		}
 
 		private void Register(string url, Func<TResourceHandler> factory) {
-			if (!Uri.TryCreate(url, UriKind.Absolute, out Uri uri)) {
+			if (!Uri.TryCreate(url, UriKind.Absolute, out var uri)) {
 				throw new ArgumentException("Resource handler URL must be absolute!");
 			}
 

lib/TweetLib.Browser.CEF/Logic/JsDialogHandlerLogic.cs

@@ -9,7 +9,7 @@ namespace TweetLib.Browser.CEF.Logic {
 			
 			int pipe = text.IndexOf('|');
 			if (pipe != -1) {
-				type = text.Substring(0, pipe) switch {
+				type = text[..pipe] switch {
 					"error"    => MessageDialogType.Error,
 					"warning"  => MessageDialogType.Warning,
 					"info"     => MessageDialogType.Information,
@@ -18,7 +18,7 @@ namespace TweetLib.Browser.CEF.Logic {
 				};
 
 				if (type != MessageDialogType.None) {
-					text = text.Substring(pipe + 1);
+					text = text[(pipe + 1)..];
 				}
 			}
 

lib/TweetLib.Browser.CEF/Utils/CefUtils.cs

@@ -8,7 +8,7 @@ namespace TweetLib.Browser.CEF.Utils {
 			return Path.Combine(storagePath, "Cache");
 		}
 
-		public static CommandLineArgs ParseCommandLineArguments(string argumentString) {
+		public static CommandLineArgs ParseCommandLineArguments(string? argumentString) {
 			CommandLineArgs args = new CommandLineArgs();
 
 			if (string.IsNullOrWhiteSpace(argumentString)) {
@@ -26,8 +26,8 @@ namespace TweetLib.Browser.CEF.Utils {
 					value = "1";
 				}
 				else {
-					key = matchValue.Substring(0, indexEquals).TrimStart('-');
+					key = matchValue[..indexEquals].TrimStart('-');
-					value = matchValue.Substring(indexEquals + 1).Trim('"');
+					value = matchValue[(indexEquals + 1)..].Trim('"');
 				}
 
 				if (key.Length != 0) {

lib/TweetLib.Browser/Contexts/Notification.cs

@@ -1,9 +1,9 @@
 namespace TweetLib.Browser.Contexts {
 	public struct Notification {
-		public string TweetUrl { get; }
+		public string? TweetUrl { get; }
 		public string? QuoteUrl { get; }
 
-		public Notification(string tweetUrl, string? quoteUrl) {
+		public Notification(string? tweetUrl, string? quoteUrl) {
 			TweetUrl = tweetUrl;
 			QuoteUrl = quoteUrl;
 		}

lib/TweetLib.Communication/Pipe/DuplexPipe.cs

@@ -13,13 +13,11 @@ namespace TweetLib.Communication.Pipe {
 
 		public static Client CreateClient(string token) {
 			int space = token.IndexOf(' ');
-			return new Client(token.Substring(0, space), token.Substring(space + 1));
+			return new Client(token[..space], token[(space + 1)..]);
 		}
 
 		private readonly PipeStream pipeIn;
 		private readonly PipeStream pipeOut;
-
-		private readonly Thread readerThread;
 		private readonly StreamWriter writerStream;
 
 		public event EventHandler<PipeReadEventArgs>? DataIn;
@@ -27,13 +25,9 @@ namespace TweetLib.Communication.Pipe {
 		private DuplexPipe(PipeStream pipeIn, PipeStream pipeOut) {
 			this.pipeIn = pipeIn;
 			this.pipeOut = pipeOut;
-
-			this.readerThread = new Thread(ReaderThread) {
-				IsBackground = true
-			};
-
-			this.readerThread.Start();
 			this.writerStream = new StreamWriter(this.pipeOut);
+
+			new Thread(ReaderThread) { IsBackground = true }.Start();
 		}
 
 		private void ReaderThread() {
@@ -95,8 +89,8 @@ namespace TweetLib.Communication.Pipe {
 					Data = string.Empty;
 				}
 				else {
-					Key = line.Substring(0, separatorIndex);
+					Key = line[..separatorIndex];
-					Data = line.Substring(separatorIndex + 1);
+					Data = line[(separatorIndex + 1)..];
 				}
 			}
 		}

lib/TweetLib.Core/Features/BaseResourceRequestHandler.cs

@@ -34,7 +34,7 @@ namespace TweetLib.Core.Features {
 			if (resourceType is ResourceType.Script or ResourceType.Stylesheet && TweetDeckHashes.Count > 0) {
 				Match match = TweetDeckResourceUrl.Match(url);
 
-				if (match.Success && TweetDeckHashes.TryGetValue($"{match.Groups[1]}.{match.Groups[3]}", out string hash)) {
+				if (match.Success && TweetDeckHashes.TryGetValue($"{match.Groups[1]}.{match.Groups[3]}", out var hash)) {
 					if (match.Groups[2].Value == hash) {
 						App.Logger.Debug("[RequestHandlerBase] Accepting " + url);
 					}

lib/TweetLib.Core/Features/FileDownloadManager.cs

@@ -84,7 +84,7 @@ namespace TweetLib.Core.Features {
 			var settings = new SaveFileDialogSettings {
 				DialogTitle = oneImage ? "Save Image" : "Save Images",
 				OverwritePrompt = oneImage,
-				FileName = qualityIndex == -1 ? filename : $"{author} {Path.ChangeExtension(filename, null)} {firstImageLink.Substring(qualityIndex + 1)}".Trim() + ext,
+				FileName = qualityIndex == -1 ? filename : $"{author} {Path.ChangeExtension(filename, null)} {firstImageLink[(qualityIndex + 1)..]}".Trim() + ext,
 				Filters = new [] { new FileDialogFilter(oneImage ? "Image" : "Images", string.IsNullOrEmpty(ext) ? Array.Empty<string>() : new [] { ext }) }
 			};
 

lib/TweetLib.Core/Features/Notifications/NotificationBrowser.Tweet.cs

@@ -56,7 +56,9 @@ namespace TweetLib.Core.Features.Notifications {
 					menu.AddSeparator();
 
 					if (context.Notification is {} notification) {
-						AddCopyAction(menu, "Copy tweet address", notification.TweetUrl);
+						if (!string.IsNullOrEmpty(notification.TweetUrl)) {
+							AddCopyAction(menu, "Copy tweet address", notification.TweetUrl);
+						}
 
 						if (!string.IsNullOrEmpty(notification.QuoteUrl)) {
 							AddCopyAction(menu, "Copy quoted tweet address", notification.QuoteUrl!);
@@ -72,7 +74,7 @@ namespace TweetLib.Core.Features.Notifications {
 				this.browserComponent.PageLoadEnd -= BrowserComponentOnPageLoadEnd;
 			}
 
-			private void BrowserComponentOnPageLoadEnd(object sender, PageLoadEventArgs e) {
+			private void BrowserComponentOnPageLoadEnd(object? sender, PageLoadEventArgs e) {
 				string url = e.Url;
 
 				if (TwitterUrls.IsTweetDeck(url) && url != BlankURL) {

lib/TweetLib.Core/Features/Plugins/Plugin.cs

@@ -93,7 +93,7 @@ namespace TweetLib.Core.Features.Plugins {
 			return Identifier.GetHashCode();
 		}
 
-		public override bool Equals(object obj) {
+		public override bool Equals(object? obj) {
 			return obj is Plugin plugin && plugin.Identifier.Equals(Identifier);
 		}
 

lib/TweetLib.Core/Features/Plugins/PluginBridge.cs

@@ -48,17 +48,17 @@ namespace TweetLib.Core.Features.Plugins {
 		}
 
 		internal Plugin? GetPluginFromToken(int token) {
-			return tokens.TryGetValue(token, out Plugin plugin) ? plugin : null;
+			return tokens.TryGetValue(token, out var plugin) ? plugin : null;
 		}
 
 		// Event handlers
 
-		private void manager_Reloaded(object sender, PluginErrorEventArgs e) {
+		private void manager_Reloaded(object? sender, PluginErrorEventArgs e) {
 			tokens.Clear();
 			fileCache.Clear();
 		}
 
-		private void Config_PluginChangedState(object sender, PluginChangedStateEventArgs e) {
+		private void Config_PluginChangedState(object? sender, PluginChangedStateEventArgs e) {
 			if (!e.IsEnabled) {
 				int token = GetTokenFromPlugin(e.Plugin);
 
@@ -88,7 +88,7 @@ namespace TweetLib.Core.Features.Plugins {
 		private string ReadFileUnsafe(int token, PluginFolder folder, string path, bool readCached) {
 			string fullPath = GetFullPathOrThrow(token, folder, path);
 
-			if (readCached && fileCache.TryGetValue(token, folder, path, out string cachedContents)) {
+			if (readCached && fileCache.TryGetValue(token, folder, path, out var cachedContents)) {
 				return cachedContents;
 			}
 
@@ -161,7 +161,7 @@ namespace TweetLib.Core.Features.Plugins {
 				cache.Clear();
 			}
 
-			public bool TryGetValue(int token, PluginFolder folder, string path, out string contents) {
+			public bool TryGetValue(int token, PluginFolder folder, string path, [MaybeNullWhen(false)] out string contents) {
 				return cache.TryGetValue(token, Key(folder, path), out contents);
 			}
 

lib/TweetLib.Core/Features/Plugins/PluginLoader.cs

@@ -41,7 +41,7 @@ namespace TweetLib.Core.Features.Plugins {
 		private static Plugin FromFolder(string name, string pathRoot, string pathData, PluginGroup group) {
 			Plugin.Builder builder = new Plugin.Builder(group, name, pathRoot, pathData);
 
-			foreach (var environment in Directory.EnumerateFiles(pathRoot, "*.js", SearchOption.TopDirectoryOnly).Select(Path.GetFileName).Select(EnvironmentFromFileName)) {
+			foreach (var environment in Directory.EnumerateFiles(pathRoot, "*.js", SearchOption.TopDirectoryOnly).Select(Path.GetFileName).Select(EnvironmentFromFileName!)) {
 				builder.AddEnvironment(environment);
 			}
 
@@ -55,7 +55,7 @@ namespace TweetLib.Core.Features.Plugins {
 			string currentContents = string.Empty;
 
 			foreach (string line in File.ReadAllLines(metaFile, Encoding.UTF8).Concat(EndTag).Select(static line => line.TrimEnd()).Where(static line => line.Length > 0)) {
-				if (line[0] == '[' && line[line.Length - 1] == ']') {
+				if (line[0] == '[' && line[^1] == ']') {
 					if (currentTag != null) {
 						SetProperty(builder, currentTag, currentContents);
 					}
@@ -106,7 +106,7 @@ namespace TweetLib.Core.Features.Plugins {
 					builder.ConfigDefault = value;
 					break;
 				case "REQUIRES":
-					builder.RequiredVersion = Version.TryParse(value, out Version version) ? version : throw new FormatException($"Invalid required minimum version: {value}");
+					builder.RequiredVersion = Version.TryParse(value, out var version) ? version : throw new FormatException($"Invalid required minimum version: {value}");
 					break;
 				default:
 					throw new FormatException($"Invalid metadata tag: {tag}");

lib/TweetLib.Core/Features/Plugins/PluginManager.cs

@@ -102,7 +102,7 @@ namespace TweetLib.Core.Features.Plugins {
 			Executed?.Invoke(this, new PluginErrorEventArgs(errors));
 		}
 
-		private void Config_PluginChangedState(object sender, PluginChangedStateEventArgs e) {
+		private void Config_PluginChangedState(object? sender, PluginChangedStateEventArgs e) {
 			browserExecutor?.RunFunction("TDPF_setPluginState", e.Plugin, e.IsEnabled);
 		}
 

lib/TweetLib.Core/Features/TweetDeck/TweetDeckBrowser.cs

@@ -71,12 +71,12 @@ namespace TweetLib.Core.Features.TweetDeck {
 			App.UserConfiguration.SoundNotificationChanged -= UserConfiguration_SoundNotificationChanged;
 		}
 
-		private void browserComponent_BrowserLoaded(object sender, BrowserLoadedEventArgs e) {
+		private void browserComponent_BrowserLoaded(object? sender, BrowserLoadedEventArgs e) {
 			e.AddDictionaryWords("tweetdeck", "TweetDeck", "tweetduck", "TweetDuck", "TD");
 			isBrowserReady = true;
 		}
 
-		private void browserComponent_PageLoadStart(object sender, PageLoadEventArgs e) {
+		private void browserComponent_PageLoadStart(object? sender, PageLoadEventArgs e) {
 			string url = e.Url;
 
 			if (TwitterUrls.IsTweetDeck(url) || (TwitterUrls.IsTwitter(url) && !TwitterUrls.IsTwitterLogin2Factor(url))) {
@@ -84,7 +84,7 @@ namespace TweetLib.Core.Features.TweetDeck {
 			}
 		}
 
-		private void browserComponent_PageLoadEnd(object sender, PageLoadEventArgs e) {
+		private void browserComponent_PageLoadEnd(object? sender, PageLoadEventArgs e) {
 			string url = e.Url;
 
 			if (TwitterUrls.IsTweetDeck(url)) {
@@ -105,7 +105,7 @@ namespace TweetLib.Core.Features.TweetDeck {
 			browserComponent.RunBootstrap("update");
 		}
 
-		private void pluginManager_Reloaded(object sender, PluginErrorEventArgs e) {
+		private void pluginManager_Reloaded(object? sender, PluginErrorEventArgs e) {
 			if (e.HasErrors) {
 				App.MessageDialogs.Error("Error Loading Plugins", "The following plugins will not be available until the issues are resolved:\n\n" + string.Join("\n\n", e.Errors));
 			}
@@ -115,14 +115,14 @@ namespace TweetLib.Core.Features.TweetDeck {
 			}
 		}
 
-		private void pluginManager_Executed(object sender, PluginErrorEventArgs e) {
+		private void pluginManager_Executed(object? sender, PluginErrorEventArgs e) {
 			if (e.HasErrors) {
 				App.MessageDialogs.Error("Error Executing Plugins", "Failed to execute the following plugins:\n\n" + string.Join("\n\n", e.Errors));
 			}
 		}
 
-		private void updateChecker_CheckFinished(object sender, UpdateCheckEventArgs e) {
+		private void updateChecker_CheckFinished(object? sender, UpdateCheckEventArgs e) {
-			var updateChecker = (UpdateChecker) sender;
+			var updateChecker = (UpdateChecker) sender!;
 
 			e.Result.Handle(update => {
 				string tag = update.VersionTag;
@@ -144,7 +144,7 @@ namespace TweetLib.Core.Features.TweetDeck {
 			ignoreUpdateCheckError = true;
 		}
 
-		private void UserConfiguration_GeneralEventHandler(object sender, EventArgs e) {
+		private void UserConfiguration_GeneralEventHandler(object? sender, EventArgs e) {
 			UpdatePropertyObject();
 		}
 

lib/TweetLib.Core/Features/TweetDeck/TweetDeckExtraContext.cs

@@ -24,15 +24,15 @@ namespace TweetLib.Core.Features.TweetDeck {
 
 			switch (type) {
 				case "link":
-					Link = new Link(url!, url!);
+					Link = new Link(url, url);
 					break;
 
 				case "image":
-					Media = new Media(Type.Image, TwitterUrls.GetMediaLink(url!, App.UserConfiguration.TwitterImageQuality));
+					Media = new Media(Type.Image, TwitterUrls.GetMediaLink(url, App.UserConfiguration.TwitterImageQuality));
 					break;
 
 				case "video":
-					Media = new Media(Type.Video, url!);
+					Media = new Media(Type.Video, url);
 					break;
 			}
 		}

lib/TweetLib.Core/Features/Twitter/ImageUrl.cs

@@ -57,7 +57,7 @@ namespace TweetLib.Core.Features.Twitter {
 				return false;
 			}
 
-			string originalUrl = url.Substring(0, question);
+			string originalUrl = url[..question];
 
 			obj = new ImageUrl(Path.HasExtension(originalUrl) ? originalUrl : originalUrl + imageExtension, imageQuality);
 			return true;

lib/TweetLib.Core/Features/Twitter/TwitterUrls.cs

@@ -49,11 +49,11 @@ namespace TweetLib.Core.Features.Twitter {
 		}
 
 		public static UrlType Check(string url) {
-			if (url.Contains("\"")) {
+			if (url.Contains('"')) {
 				return UrlType.Invalid;
 			}
 
-			if (Uri.TryCreate(url, UriKind.Absolute, out Uri uri)) {
+			if (Uri.TryCreate(url, UriKind.Absolute, out var uri)) {
 				string scheme = uri.Scheme;
 
 				if (scheme == Uri.UriSchemeHttps || scheme == Uri.UriSchemeHttp || scheme == Uri.UriSchemeFtp || scheme == Uri.UriSchemeMailto) {

lib/TweetLib.Core/Systems/Configuration/ConfigManager.cs

@@ -16,7 +16,7 @@ namespace TweetLib.Core.Systems.Configuration {
 			ConverterRegistry.Register(typeof(WindowState), new BasicTypeConverter<WindowState> {
 				ConvertToString = static value => $"{(value.IsMaximized ? 'M' : '_')}{value.Bounds.X} {value.Bounds.Y} {value.Bounds.Width} {value.Bounds.Height}",
 				ConvertToObject = static value => {
-					int[] elements = StringUtils.ParseInts(value.Substring(1), ' ');
+					int[] elements = StringUtils.ParseInts(value[1..], ' ');
 
 					return new WindowState {
 						Bounds = new Rectangle(elements[0], elements[1], elements[2], elements[3]),

lib/TweetLib.Core/Systems/Logging/Logger.cs

@@ -43,7 +43,7 @@ namespace TweetLib.Core.Systems.Logging {
 				build.Append("Please, report all issues to: ").Append(Lib.IssueTrackerUrl).Append("\r\n\r\n");
 			}
 
-			build.Append("[").Append(DateTime.Now.ToString("G", Lib.Culture)).Append("] ").Append(level).Append("\r\n");
+			build.Append('[').Append(DateTime.Now.ToString("G", Lib.Culture)).Append("] ").Append(level).Append("\r\n");
 			build.Append(message).Append("\r\n\r\n");
 
 			try {

lib/TweetLib.Core/Systems/Updates/UpdateChecker.cs

@@ -37,7 +37,7 @@ namespace TweetLib.Core.Systems.Updates {
 			InteractionManager.Dispose();
 		}
 
-		private void timer_Elapsed(object sender, ElapsedEventArgs e) {
+		private void timer_Elapsed(object? sender, ElapsedEventArgs e) {
 			Check(false);
 		}
 

lib/TweetLib.Core/Systems/Updates/UpdateInteractionManager.cs

@@ -26,7 +26,7 @@ namespace TweetLib.Core.Systems.Updates {
 			nextUpdate = null;
 		}
 
-		private void updates_CheckFinished(object sender, UpdateCheckEventArgs e) {
+		private void updates_CheckFinished(object? sender, UpdateCheckEventArgs e) {
 			UpdateInfo? foundUpdate = e.Result.HasValue ? e.Result.Value : null;
 
 			if (nextUpdate != null && !nextUpdate.Equals(foundUpdate)) {

lib/TweetLib.Utils/Collections/CommandLineArgs.cs

@@ -57,7 +57,7 @@ namespace TweetLib.Utils.Collections {
 		}
 
 		public string? GetValue(string key) {
-			return values.TryGetValue(key.ToLower(), out string val) ? val : null;
+			return values.TryGetValue(key.ToLower(), out var val) ? val : null;
 		}
 
 		public void RemoveValue(string key) {

lib/TweetLib.Utils/Collections/TwoKeyDictionary.cs

@@ -11,7 +11,7 @@ namespace TweetLib.Utils.Collections {
 	/// <typeparam name="V">The type of the values.</typeparam>
 	[SuppressMessage("ReSharper", "UnusedMethodReturnValue.Global")]
 	[SuppressMessage("ReSharper", "UnusedMember.Global")]
-	public sealed class TwoKeyDictionary<K1, K2, V> {
+	public sealed class TwoKeyDictionary<K1, K2, V> where K1 : notnull where K2 : notnull {
 		private readonly Dictionary<K1, Dictionary<K2, V>> dict;
 		private readonly int innerCapacity;
 
@@ -41,7 +41,7 @@ namespace TweetLib.Utils.Collections {
 			}
 
 			set {
-				if (!dict.TryGetValue(outerKey, out Dictionary<K2, V> innerDict)) {
+				if (!dict.TryGetValue(outerKey, out Dictionary<K2, V>? innerDict)) {
 					dict.Add(outerKey, innerDict = new Dictionary<K2, V>(innerCapacity));
 				}
 
@@ -67,7 +67,7 @@ namespace TweetLib.Utils.Collections {
 		/// Throws if the key pair already exists.
 		/// </summary>
 		public void Add(K1 outerKey, K2 innerKey, V value) {
-			if (!dict.TryGetValue(outerKey, out Dictionary<K2, V> innerDict)) {
+			if (!dict.TryGetValue(outerKey, out Dictionary<K2, V>? innerDict)) {
 				dict.Add(outerKey, innerDict = new Dictionary<K2, V>(innerCapacity));
 			}
 
@@ -100,7 +100,7 @@ namespace TweetLib.Utils.Collections {
 		/// Determines whether the dictionary contains the key pair.
 		/// </summary>
 		public bool Contains(K1 outerKey, K2 innerKey) {
-			return dict.TryGetValue(outerKey, out Dictionary<K2, V> innerDict) && innerDict.ContainsKey(innerKey);
+			return dict.TryGetValue(outerKey, out Dictionary<K2, V>? innerDict) && innerDict.ContainsKey(innerKey);
 		}
 
 		/// <summary>
@@ -122,8 +122,8 @@ namespace TweetLib.Utils.Collections {
 		/// Gets the value associated with the key pair.
 		/// Returns true if the key pair was present.
 		/// </summary>
-		public bool TryGetValue(K1 outerKey, K2 innerKey, out V value) {
+		public bool TryGetValue(K1 outerKey, K2 innerKey, [MaybeNullWhen(false)] out V value) {
-			if (dict.TryGetValue(outerKey, out Dictionary<K2, V> innerDict)) {
+			if (dict.TryGetValue(outerKey, out Dictionary<K2, V>? innerDict)) {
 				return innerDict.TryGetValue(innerKey, out value);
 			}
 			else {
@@ -145,7 +145,7 @@ namespace TweetLib.Utils.Collections {
 		/// Returns true if the key pair was present.
 		/// </summary>
 		public bool Remove(K1 outerKey, K2 innerKey) {
-			if (dict.TryGetValue(outerKey, out Dictionary<K2, V> innerDict) && innerDict.Remove(innerKey)) {
+			if (dict.TryGetValue(outerKey, out Dictionary<K2, V>? innerDict) && innerDict.Remove(innerKey)) {
 				if (innerDict.Count == 0) {
 					dict.Remove(outerKey);
 				}

lib/TweetLib.Utils/Dialogs/SaveFileDialogSettings.cs

@@ -2,9 +2,9 @@ using System.Collections.Generic;
 
 namespace TweetLib.Utils.Dialogs {
 	public sealed class SaveFileDialogSettings {
-		public string DialogTitle { get; set; } = "Save File";
+		public string DialogTitle { get; init; } = "Save File";
-		public bool OverwritePrompt { get; set; } = true;
+		public bool OverwritePrompt { get; init; } = true;
-		public string? FileName { get; set; }
+		public string? FileName { get; init; }
-		public IReadOnlyList<FileDialogFilter>? Filters { get; set; }
+		public IReadOnlyList<FileDialogFilter>? Filters { get; init; }
 	}
 }

lib/TweetLib.Utils/Globalization/Language.cs

@@ -21,7 +21,7 @@ namespace TweetLib.Utils.Globalization {
 			}
 		}
 
-		public override bool Equals(object obj) {
+		public override bool Equals(object? obj) {
 			return obj is Language other && Code.Equals(other.Code, StringComparison.OrdinalIgnoreCase);
 		}
 
@@ -38,8 +38,8 @@ namespace TweetLib.Utils.Globalization {
 			return cultureInfo.DisplayName == cultureInfo.NativeName ? capitalizedName : $"{capitalizedName}, {cultureInfo.DisplayName}";
 		}
 
-		public int CompareTo(Language other) {
+		public int CompareTo(Language? other) {
-			return string.Compare(Name, other.Name, false, CultureInfo.InvariantCulture);
+			return string.Compare(Name, other?.Name, false, CultureInfo.InvariantCulture);
 		}
 	}
 }

lib/TweetLib.Utils/IO/CombinedFileStream.cs

@@ -134,7 +134,7 @@ namespace TweetLib.Utils.IO {
 			public string[] KeyValue {
 				get {
 					int index = Identifier.IndexOf(KeySeparator);
-					return index == -1 ? StringUtils.EmptyArray : Identifier.Substring(index + 1).Split(KeySeparator);
+					return index == -1 ? StringUtils.EmptyArray : Identifier[(index + 1)..].Split(KeySeparator);
 				}
 			}
 

lib/TweetLib.Utils/Serialization/Converters/BasicTypeConverter.cs

@@ -2,12 +2,12 @@
 
 namespace TweetLib.Utils.Serialization.Converters {
 	public sealed class BasicTypeConverter<T> : ITypeConverter {
-		public Func<T, string>? ConvertToString { get; set; }
+		public Func<T, string>? ConvertToString { get; init; }
-		public Func<string, T>? ConvertToObject { get; set; }
+		public Func<string, T>? ConvertToObject { get; init; }
 
-		bool ITypeConverter.TryWriteType(Type type, object value, out string? converted) {
+		bool ITypeConverter.TryWriteType(Type type, object? value, out string? converted) {
 			try {
-				converted = ConvertToString!((T) value);
+				converted = ConvertToString!((T) value!);
 				return true;
 			} catch {
 				converted = null;

lib/TweetLib.Utils/Serialization/Converters/ClrTypeConverter.cs

@@ -6,18 +6,17 @@ namespace TweetLib.Utils.Serialization.Converters {
 
 		private ClrTypeConverter() {}
 
-		bool ITypeConverter.TryWriteType(Type type, object value, out string? converted) {
+		bool ITypeConverter.TryWriteType(Type type, object? value, out string? converted) {
 			switch (Type.GetTypeCode(type)) {
 				case TypeCode.Boolean:
-					converted = value.ToString();
+					converted = value!.ToString();
 					return true;
 
 				case TypeCode.Int32:
-					converted = ((int) value).ToString(); // cast required for enums
+					converted = ((int) value!).ToString(); // cast required for enums
 					return true;
 
 				case TypeCode.String:
-					// ReSharper disable once ConstantConditionalAccessQualifier
 					converted = value?.ToString();
 					return true;
 

lib/TweetLib.Utils/Serialization/ITypeConverter.cs

@@ -2,7 +2,7 @@
 
 namespace TweetLib.Utils.Serialization {
 	public interface ITypeConverter {
-		bool TryWriteType(Type type, object value, out string? converted);
+		bool TryWriteType(Type type, object? value, out string? converted);
 		bool TryReadType(Type type, string value, out object? converted);
 	}
 }

lib/TweetLib.Utils/Serialization/SimpleObjectSerializer.cs

@@ -28,7 +28,7 @@ namespace TweetLib.Utils.Serialization {
 					break;
 				}
 				else {
-					build.Append(data.Substring(index, nextIndex - index));
+					build.Append(data[index..nextIndex]);
 
 					char next = data[nextIndex + 1];
 
@@ -47,7 +47,7 @@ namespace TweetLib.Utils.Serialization {
 				}
 			}
 
-			return build.Append(data.Substring(index)).ToString();
+			return build.Append(data[index..]).ToString();
 		}
 
 		private readonly TypeConverterRegistry converterRegistry;
@@ -114,7 +114,7 @@ namespace TweetLib.Utils.Serialization {
 				int nextPos = contents.IndexOf(NewLineReal, currentPos);
 
 				if (nextPos == -1) {
-					line = contents.Substring(currentPos);
+					line = contents[currentPos..];
 					currentPos = -1;
 
 					if (string.IsNullOrEmpty(line)) {
@@ -133,10 +133,10 @@ namespace TweetLib.Utils.Serialization {
 					continue;
 				}
 
-				string property = line.Substring(0, space);
+				string property = line[..space];
-				string value = UnescapeLine(line.Substring(space + 1));
+				string value = UnescapeLine(line[(space + 1)..]);
 
-				if (props.TryGetValue(property, out PropertyInfo info)) {
+				if (props.TryGetValue(property, out var info)) {
 					var type = info.PropertyType;
 					var converter = converterRegistry.TryGet(type) ?? ClrTypeConverter.Instance;
 

lib/TweetLib.Utils/Startup/LockFile.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Threading;
 using TweetLib.Utils.Static;
@@ -91,7 +90,6 @@ namespace TweetLib.Utils.Startup {
 			return UnlockResult.Success;
 		}
 
-		[SuppressMessage("ReSharper", "PossibleNullReferenceException")]
 		private LockResult DetermineLockingProcessOrFail(Exception originalException) {
 			try {
 				int pid;
@@ -110,7 +108,7 @@ namespace TweetLib.Utils.Startup {
 					var foundProcess = Process.GetProcessById(pid);
 					using var currentProcess = Process.GetCurrentProcess();
 
-					if (currentProcess.MainModule.FileVersionInfo.InternalName == foundProcess.MainModule.FileVersionInfo.InternalName) {
+					if (currentProcess.MainModule!.FileVersionInfo.InternalName == foundProcess.MainModule!.FileVersionInfo.InternalName) {
 						return new LockResult.HasProcess(foundProcess);
 					}
 					else {

lib/TweetLib.Utils/Static/StringUtils.cs

@@ -40,7 +40,7 @@ namespace TweetLib.Utils.Static {
 				return null;
 			}
 
-			return (str.Substring(0, index), str.Substring(index + 1));
+			return (str[..index], str[(index + 1)..]);
 		}
 
 		/// <summary>
@@ -49,7 +49,7 @@ namespace TweetLib.Utils.Static {
 		/// </summary>
 		public static string ExtractBefore(string str, char search, int startIndex = 0) {
 			int index = str.IndexOf(search, startIndex);
-			return index == -1 ? str : str.Substring(0, index);
+			return index == -1 ? str : str[..index];
 		}
 
 		/// <summary>

lib/TweetLib.Utils/Static/WebUtils.cs

@@ -12,8 +12,10 @@ namespace TweetLib.Utils.Static {
 
 		private static void EnsureTLS12() {
 			if (!hasMicrosoftBeenBroughtTo2008Yet) {
+				#pragma warning disable CS0618
 				ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12;
 				ServicePointManager.SecurityProtocol &= ~(SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11);
+				#pragma warning restore CS0618
 				hasMicrosoftBeenBroughtTo2008Yet = true;
 			}
 		}

lib/TweetTest.Core/Features/Twitter/TestTwitterUrls.fs

@@ -47,7 +47,7 @@ module RegexAccount =
             Assert.True(isMatch("https://twitter.com/" + name))
 
     module Match =
-        let extract str = TwitterUrls.RegexAccount.Match(str).Groups.[1].Value
+        let extract str = TwitterUrls.RegexAccount.Match(str).Groups[1].Value
 
         [<Fact>]
         let ``extracts account name from simple URL`` () =

lib/TweetTest.Utils/Collections/TestCommandLineArgs.fs

@@ -276,11 +276,11 @@ module ToDictionary =
         TestData.mixed.ToDictionary(dict)
 
         Assert.Equal(5, dict.Count)
-        Assert.Equal("1", dict.["flag1"])
+        Assert.Equal("1", dict["flag1"])
-        Assert.Equal("1", dict.["flag2"])
+        Assert.Equal("1", dict["flag2"])
-        Assert.Equal("1", dict.["flag3"])
+        Assert.Equal("1", dict["flag3"])
-        Assert.Equal("hello", dict.["val1"])
+        Assert.Equal("hello", dict["val1"])
-        Assert.Equal("world", dict.["val2"])
+        Assert.Equal("world", dict["val2"])
 
     [<Fact>]
     let ``prefers value if the same name is used for a flag and value`` () =
@@ -288,7 +288,7 @@ module ToDictionary =
         TestData.duplicate.ToDictionary(dict)
 
         Assert.Equal(1, dict.Count)
-        Assert.Equal("value", dict.["duplicate"])
+        Assert.Equal("value", dict["duplicate"])
 
 
 module ToString =

lib/TweetTest.Utils/Collections/TestTwoKeyDictionary.fs

@@ -38,36 +38,36 @@ module Indexer =
     [<InlineData("second", 2, 200.0)>]
     [<InlineData("third", 1, 1000.0)>]
     let ``get returns correct value`` (outerKey: string, innerKey: int, value: float) =
-        Assert.Equal(value, TestData.uniquevals.[outerKey, innerKey])
+        Assert.Equal(value, TestData.uniquevals[outerKey, innerKey])
 
     [<Fact>]
     let ``get throws if outer key is missing`` () =
-        Assert.Throws<KeyNotFoundException>(fun () -> TestData.uniquevals.["missing", 1] |> ignore)
+        Assert.Throws<KeyNotFoundException>(fun () -> TestData.uniquevals["missing", 1] |> ignore)
 
     [<Fact>]
     let ``get throws if inner key is missing`` () =
-        Assert.Throws<KeyNotFoundException>(fun () -> TestData.uniquevals.["first", 0] |> ignore)
+        Assert.Throws<KeyNotFoundException>(fun () -> TestData.uniquevals["first", 0] |> ignore)
 
     [<Fact>]
     let ``set modifies existing value`` () =
         let copy = TestData.uniquevals
-        copy.["first", 1] <- 50.0
+        copy["first", 1] <- 50.0
 
-        Assert.Equal(50.0, copy.["first", 1])
+        Assert.Equal(50.0, copy["first", 1])
 
     [<Fact>]
     let ``set creates new inner key`` () =
         let copy = TestData.uniquevals
-        copy.["second", 3] <- 300.0
+        copy["second", 3] <- 300.0
 
-        Assert.Equal(300.0, copy.["second", 3])
+        Assert.Equal(300.0, copy["second", 3])
 
     [<Fact>]
     let ``set creates new outer key`` () =
         let copy = TestData.uniquevals
-        copy.["fourth", 1] <- 10000.0
+        copy["fourth", 1] <- 10000.0
 
-        Assert.Equal(10000.0, copy.["fourth", 1])
+        Assert.Equal(10000.0, copy["fourth", 1])
 
 
 module InnerValues =
@@ -93,14 +93,14 @@ module Add =
         let copy = TestData.uniquevals
         copy.Add("first", 4, 40.0)
 
-        Assert.Equal(40.0, copy.["first", 4])
+        Assert.Equal(40.0, copy["first", 4])
 
     [<Fact>]
     let ``creates new outer key`` () =
         let copy = TestData.uniquevals
         copy.Add("fourth", 1, 10000.0)
 
-        Assert.Equal(10000.0, copy.["fourth", 1])
+        Assert.Equal(10000.0, copy["fourth", 1])
 
     [<Fact>]
     let ``throw on duplicate key`` () =

lib/TweetTest.Utils/IO/TestCombinedFileStream.fs

@@ -83,7 +83,7 @@ module ReadFile =
     [<InlineData("singleFile")>]
     [<InlineData("singleFileWithMultiIdentifier")>]
     let ``reading first file from single file stream returns an entry`` (stream: string) =
-        using TestData.singleFileStreams.[stream] (fun f ->
+        using TestData.singleFileStreams[stream] (fun f ->
             Assert.NotNull(f.ReadFile())
         )
 
@@ -91,7 +91,7 @@ module ReadFile =
     [<InlineData("singleFile")>]
     [<InlineData("singleFileWithMultiIdentifier")>]
     let ``reading second file from single file stream returns null`` (stream: string) =
-        using TestData.singleFileStreams.[stream] (fun f ->
+        using TestData.singleFileStreams[stream] (fun f ->
             f.ReadFile() |> ignore
             Assert.Null(f.ReadFile())
         )
@@ -197,7 +197,7 @@ module Entry =
         [<InlineData("singleFile")>]
         [<InlineData("singleFileWithMultiIdentifier")>]
         let ``contents of single file stream with are correct`` (stream: string) =
-            using TestData.singleFileStreams.[stream] (fun f ->
+            using TestData.singleFileStreams[stream] (fun f ->
                 Assert.Equal("test file\n123", Encoding.UTF8.GetString(f.ReadFile().Contents))
             )
 

windows/TweetDuck.Browser/Program.cs

@@ -25,7 +25,7 @@ namespace TweetDuck.Browser {
 		private static async void KillWhenHung(int parentId) {
 			try {
 				using Process process = Process.GetProcessById(parentId);
-				process.WaitForExit();
+				await process.WaitForExitAsync();
 			} catch {
 				// ded
 			}

windows/TweetDuck.Video/Controls/LabelTooltip.cs

@@ -30,7 +30,7 @@ namespace TweetDuck.Video.Controls {
 
 				Text = text;
 
-				Point loc = form!.PointToClient(control.Parent.PointToScreen(new Point(control.Location.X + (followCursor ? args.X : control.Width / 2), 0)));
+				Point loc = form.PointToClient(control.Parent.PointToScreen(new Point(control.Location.X + (followCursor ? args.X : control.Width / 2), 0)));
 				loc.X = Math.Max(0, Math.Min(form.Width - Width, loc.X - Width / 2));
 				loc.Y -= Height - Margin.Top + Margin.Bottom;
 				Location = loc;
@@ -42,7 +42,7 @@ namespace TweetDuck.Video.Controls {
 			control.MouseLeave += control_MouseLeave;
 		}
 
-		private void control_MouseLeave(object sender, EventArgs e) {
+		private void control_MouseLeave(object? sender, EventArgs e) {
 			Visible = false;
 		}
 	}

windows/TweetDuck.Video/FormPlayer.cs

@@ -153,12 +153,12 @@ namespace TweetDuck.Video {
 
 		// Events
 
-		private void FormPlayer_Load(object sender, EventArgs e) {
+		private void FormPlayer_Load(object? sender, EventArgs e) {
 			Player.URL = videoUrl;
 		}
 
-		private void pipe_DataIn(object sender, DuplexPipe.PipeReadEventArgs e) {
+		private void pipe_DataIn(object? sender, DuplexPipe.PipeReadEventArgs e) {
-			Invoke(new Action(() => {
+			Invoke(() => {
 				switch (e.Key) {
 					case "key":
 						HandleKey((Keys) int.Parse(e.Data, NumberStyles.Integer));
@@ -168,7 +168,7 @@ namespace TweetDuck.Video {
 						StopVideo();
 						break;
 				}
-			}));
+			});
 		}
 
 		private void player_PlayStateChange(int newState) {
@@ -215,7 +215,7 @@ namespace TweetDuck.Video {
 			Marshal.ReleaseComObject(controls);
 		}
 
-		private void timerSync_Tick(object sender, EventArgs e) {
+		private void timerSync_Tick(object? sender, EventArgs e) {
 			if (NativeMethods.GetWindowRect(ownerHandle, out NativeMethods.RECT rect)) {
 				IWMPMedia media = Player.currentMedia;
 				IWMPControls controls = Player.controls;
@@ -312,12 +312,12 @@ namespace TweetDuck.Video {
 			}
 		}
 
-		private void timerData_Tick(object sender, EventArgs e) {
+		private void timerData_Tick(object? sender, EventArgs e) {
 			timerData.Stop();
 			pipe.Write("vol", trackBarVolume.Value.ToString());
 		}
 
-		private void progressSeek_MouseDown(object sender, MouseEventArgs e) {
+		private void progressSeek_MouseDown(object? sender, MouseEventArgs e) {
 			if (e.Button == MouseButtons.Left) {
 				IWMPMedia media = Player.currentMedia;
 				IWMPControls controls = Player.controls;
@@ -329,7 +329,7 @@ namespace TweetDuck.Video {
 			}
 		}
 
-		private void trackBarVolume_ValueChanged(object sender, EventArgs e) {
+		private void trackBarVolume_ValueChanged(object? sender, EventArgs e) {
 			IWMPSettings settings = Player.settings;
 			settings.volume = trackBarVolume.Value;
 
@@ -341,23 +341,23 @@ namespace TweetDuck.Video {
 			}
 		}
 
-		private void trackBarVolume_MouseDown(object sender, MouseEventArgs e) {
+		private void trackBarVolume_MouseDown(object? sender, MouseEventArgs e) {
 			isDragging = true;
 		}
 
-		private void trackBarVolume_MouseUp(object sender, MouseEventArgs e) {
+		private void trackBarVolume_MouseUp(object? sender, MouseEventArgs e) {
 			isDragging = false;
 		}
 
-		private void imageClose_Click(object sender, EventArgs e) {
+		private void imageClose_Click(object? sender, EventArgs e) {
 			StopVideo();
 		}
 
-		private void imageDownload_Click(object sender, EventArgs e) {
+		private void imageDownload_Click(object? sender, EventArgs e) {
 			pipe.Write("download");
 		}
 
-		private void imageResize_Click(object sender, EventArgs e) {
+		private void imageResize_Click(object? sender, EventArgs e) {
 			Player.fullScreen = true;
 		}
 

windows/TweetDuck/Application/FileDialogs.cs

@@ -18,7 +18,7 @@ namespace TweetDuck.Application {
 				};
 
 				if (dialog.ShowDialog() == DialogResult.OK) {
-					onAccepted(dialog.FileName);
+					onAccepted(dialog.FileName!);
 				}
 			});
 		}

windows/TweetDuck/Application/SystemHandler.cs

@@ -13,7 +13,7 @@ using TweetLib.Core.Systems.Configuration;
 
 namespace TweetDuck.Application {
 	sealed class SystemHandler : IAppSystemHandler {
-		public void OpenBrowser(string url) {
+		public void OpenBrowser(string? url) {
 			if (string.IsNullOrWhiteSpace(url)) {
 				return;
 			}
@@ -23,7 +23,7 @@ namespace TweetDuck.Application {
 
 				switch (TwitterUrls.Check(url)) {
 					case TwitterUrls.UrlType.Fine:
-						string browserPath = config.BrowserPath;
+						string? browserPath = config.BrowserPath;
 
 						if (browserPath == null || !File.Exists(browserPath)) {
 							OpenAssociatedProgram(url);
@@ -120,7 +120,7 @@ namespace TweetDuck.Application {
 
 			void PerformSearch() {
 				var config = Program.Config.User;
-				string searchUrl = config.SearchEngineUrl;
+				string? searchUrl = config.SearchEngineUrl;
 
 				if (string.IsNullOrEmpty(searchUrl)) {
 					if (FormMessage.Question("Search Options", "You have not configured a default search engine yet, would you like to do it now?", FormMessage.Yes, FormMessage.No)) {
@@ -132,7 +132,7 @@ namespace TweetDuck.Application {
 							return;
 						}
 
-						FormSettings settings = FormManager.TryFind<FormSettings>();
+						FormSettings? settings = FormManager.TryFind<FormSettings>();
 
 						if (settings == null) {
 							return;
@@ -146,7 +146,7 @@ namespace TweetDuck.Application {
 					}
 				}
 				else {
-					App.SystemHandler.OpenBrowser(searchUrl + Uri.EscapeUriString(text));
+					App.SystemHandler.OpenBrowser(searchUrl + Uri.EscapeDataString(text));
 				}
 			}
 

windows/TweetDuck/Browser/Base/CefBrowserComponent.cs

@@ -10,7 +10,7 @@ namespace TweetDuck.Browser.Base {
 
 		public override string CacheFolder => CefUtils.GetCacheFolder(App.StoragePath);
 		
-		public CefBrowserComponent(ChromiumWebBrowser browser, CreateContextMenu createContextMenu = null, bool autoReload = true) : base(browser, createContextMenu ?? DefaultContextMenuFactory, new JsDialogOpener(browser), PopupHandler.Instance, autoReload) {
+		public CefBrowserComponent(ChromiumWebBrowser browser, CreateContextMenu? createContextMenu = null, bool autoReload = true) : base(browser, createContextMenu ?? DefaultContextMenuFactory, new JsDialogOpener(browser), PopupHandler.Instance, autoReload) {
 			browser.SetupZoomEvents();	
 		}
 	}

windows/TweetDuck/Browser/Base/ContextMenuBase.cs

@@ -14,7 +14,7 @@ namespace TweetDuck.Browser.Base {
 
 		protected static UserConfig Config => Program.Config.User;
 
-		public ContextMenuBase(IContextMenuHandler handler) : base(handler) {}
+		public ContextMenuBase(IContextMenuHandler? handler) : base(handler) {}
 
 		protected override Context CreateContext(IContextMenuParams parameters) {
 			return CreateContext(parameters, null, Config.TwitterImageQuality);
@@ -55,7 +55,7 @@ namespace TweetDuck.Browser.Base {
 			}
 		}
 
-		protected static Context CreateContext(IContextMenuParams parameters, TweetDeckExtraContext extraContext, ImageQuality imageQuality) {
+		protected static Context CreateContext(IContextMenuParams parameters, TweetDeckExtraContext? extraContext, ImageQuality imageQuality) {
 			var context = new Context();
 			var flags = parameters.TypeFlags;
 
@@ -74,7 +74,7 @@ namespace TweetDuck.Browser.Base {
 			return context;
 		}
 
-		private static Link? GetLink(IContextMenuParams parameters, TweetDeckExtraContext extraContext) {
+		private static Link? GetLink(IContextMenuParams parameters, TweetDeckExtraContext? extraContext) {
 			var link = extraContext?.Link;
 			if (link != null) {
 				return link;
@@ -87,7 +87,7 @@ namespace TweetDuck.Browser.Base {
 			return null;
 		}
 
-		private static Media? GetMedia(IContextMenuParams parameters, TweetDeckExtraContext extraContext, ImageQuality imageQuality) {
+		private static Media? GetMedia(IContextMenuParams parameters, TweetDeckExtraContext? extraContext, ImageQuality imageQuality) {
 			var media = extraContext?.Media;
 			if (media != null) {
 				return media;

windows/TweetDuck/Browser/Base/ContextMenuBrowser.cs

@@ -24,7 +24,7 @@ namespace TweetDuck.Browser.Base {
 		private readonly FormBrowser form;
 		private readonly TweetDeckExtraContext extraContext;
 
-		public ContextMenuBrowser(FormBrowser form, IContextMenuHandler handler, TweetDeckExtraContext extraContext) : base(handler) {
+		public ContextMenuBrowser(FormBrowser form, IContextMenuHandler? handler, TweetDeckExtraContext extraContext) : base(handler) {
 			this.form = form;
 			this.extraContext = extraContext;
 		}

windows/TweetDuck/Browser/Base/ContextMenuNotification.cs

@@ -8,7 +8,7 @@ namespace TweetDuck.Browser.Base {
 	sealed class ContextMenuNotification : ContextMenuBase {
 		private readonly FormNotificationBase form;
 
-		public ContextMenuNotification(FormNotificationBase form, IContextMenuHandler handler) : base(handler) {
+		public ContextMenuNotification(FormNotificationBase form, IContextMenuHandler? handler) : base(handler) {
 			this.form = form;
 		}
 

windows/TweetDuck/Browser/Base/CustomKeyboardHandler.cs

@@ -5,9 +5,9 @@ using TweetLib.Utils.Static;
 
 namespace TweetDuck.Browser.Base {
 	sealed class CustomKeyboardHandler : IKeyboardHandler {
-		private readonly IBrowserKeyHandler handler;
+		private readonly IBrowserKeyHandler? handler;
 
-		public CustomKeyboardHandler(IBrowserKeyHandler handler) {
+		public CustomKeyboardHandler(IBrowserKeyHandler? handler) {
 			this.handler = handler;
 		}
 

windows/TweetDuck/Browser/FormBrowser.cs

@@ -49,7 +49,7 @@ namespace TweetDuck.Browser {
 			}
 		}
 
-		public UpdateInstaller UpdateInstaller { get; private set; }
+		public UpdateInstaller? UpdateInstaller { get; private set; }
 
 		private readonly ResourceCache resourceCache;
 		private readonly TweetDeckBrowser browser;
@@ -63,8 +63,8 @@ namespace TweetDuck.Browser {
 		private bool isLoaded;
 		private FormWindowState prevState;
 
-		private TweetScreenshotManager notificationScreenshotManager;
+		private TweetScreenshotManager? notificationScreenshotManager;
-		private VideoPlayer videoPlayer;
+		private VideoPlayer? videoPlayer;
 
 		public FormBrowser(ResourceCache resourceCache, PluginManager pluginManager, IUpdateCheckClient updateCheckClient, uint windowRestoreMessage) {
 			InitializeComponent();
@@ -156,11 +156,11 @@ namespace TweetDuck.Browser {
 
 		// event handlers
 
-		private void timerResize_Tick(object sender, EventArgs e) {
+		private void timerResize_Tick(object? sender, EventArgs e) {
 			FormBrowser_ResizeEnd(this, e); // also stops timer
 		}
 
-		private void FormBrowser_Activated(object sender, EventArgs e) {
+		private void FormBrowser_Activated(object? sender, EventArgs e) {
 			if (!isLoaded) {
 				return;
 			}
@@ -172,7 +172,7 @@ namespace TweetDuck.Browser {
 			}                           // the window, enable the browser again
 		}
 
-		private void FormBrowser_LocationChanged(object sender, EventArgs e) {
+		private void FormBrowser_LocationChanged(object? sender, EventArgs e) {
 			if (!isLoaded) {
 				return;
 			}
@@ -181,7 +181,7 @@ namespace TweetDuck.Browser {
 			timerResize.Start();
 		}
 
-		private void FormBrowser_Resize(object sender, EventArgs e) {
+		private void FormBrowser_Resize(object? sender, EventArgs e) {
 			if (!isLoaded) {
 				return;
 			}
@@ -204,7 +204,7 @@ namespace TweetDuck.Browser {
 			}
 		}
 
-		private void FormBrowser_ResizeEnd(object sender, EventArgs e) { // also triggers when the window moves
+		private void FormBrowser_ResizeEnd(object? sender, EventArgs e) { // also triggers when the window moves
 			if (!isLoaded) {
 				return;
 			}
@@ -218,7 +218,7 @@ namespace TweetDuck.Browser {
 			}
 		}
 
-		private void FormBrowser_FormClosing(object sender, FormClosingEventArgs e) {
+		private void FormBrowser_FormClosing(object? sender, FormClosingEventArgs e) {
 			if (!isLoaded) {
 				return;
 			}
@@ -229,33 +229,33 @@ namespace TweetDuck.Browser {
 			}
 		}
 
-		private void FormBrowser_FormClosed(object sender, FormClosedEventArgs e) {
+		private void FormBrowser_FormClosed(object? sender, FormClosedEventArgs e) {
 			if (isLoaded && UpdateInstaller == null) {
 				updates.InteractionManager.ClearUpdate();
 				updates.InteractionManager.Dispose();
 			}
 		}
 
-		private void Config_MuteToggled(object sender, EventArgs e) {
+		private void Config_MuteToggled(object? sender, EventArgs e) {
 			UpdateFormIcon();
 		}
 
-		private void Config_TrayBehaviorChanged(object sender, EventArgs e) {
+		private void Config_TrayBehaviorChanged(object? sender, EventArgs e) {
 			UpdateTray();
 		}
 
-		private void trayIcon_ClickRestore(object sender, EventArgs e) {
+		private void trayIcon_ClickRestore(object? sender, EventArgs e) {
 			Show();
 			RestoreWindow();
 			Activate();
 			UpdateTray();
 		}
 
-		private void trayIcon_ClickClose(object sender, EventArgs e) {
+		private void trayIcon_ClickClose(object? sender, EventArgs e) {
 			ForceClose();
 		}
 
-		private void updateInteractionManager_UpdateAccepted(object sender, UpdateInfo update) {
+		private void updateInteractionManager_UpdateAccepted(object? sender, UpdateInfo update) {
 			this.InvokeAsyncSafe(() => {
 				FormManager.CloseAllDialogs();
 
@@ -305,7 +305,7 @@ namespace TweetDuck.Browser {
 			});
 		}
 
-		private void updateInteractionManager_UpdateDismissed(object sender, UpdateInfo update) {
+		private void updateInteractionManager_UpdateDismissed(object? sender, UpdateInfo update) {
 			this.InvokeAsyncSafe(() => {
 				Config.DismissedUpdate = update.VersionTag;
 				Config.Save();
@@ -385,7 +385,7 @@ namespace TweetDuck.Browser {
 			OpenSettings(null);
 		}
 
-		public void OpenSettings(Type startTab) {
+		public void OpenSettings(Type? startTab) {
 			if (!FormManager.TryBringToFront<FormSettings>()) {
 				bool prevEnableUpdateCheck = Config.EnableUpdateCheck;
 
@@ -464,7 +464,7 @@ namespace TweetDuck.Browser {
 				videoUrl = Regex.Replace(videoUrl, "^https://", "http://");
 			}
 
-			string playerPath = Config.VideoPlayerPath;
+			string? playerPath = Config.VideoPlayerPath;
 
 			if (playerPath == null || !File.Exists(playerPath)) {
 				if (videoPlayer == null) {
@@ -512,7 +512,7 @@ namespace TweetDuck.Browser {
 			notificationScreenshotManager.Trigger(html, width);
 		}
 
-		private void DisplayTooltip(string text) {
+		private void DisplayTooltip(string? text) {
 			if (string.IsNullOrEmpty(text)) {
 				toolTip.Hide(this);
 			}
@@ -554,7 +554,7 @@ namespace TweetDuck.Browser {
 				FormMessage.Show("TweetDuck Browser Message", contents, icon, FormMessage.OK);
 			}
 
-			public void DisplayTooltip(string text) {
+			public void DisplayTooltip(string? text) {
 				form.InvokeAsyncSafe(() => form.DisplayTooltip(text));
 			}
 

windows/TweetDuck/Browser/Notification/FormNotificationBase.cs

@@ -97,11 +97,11 @@ namespace TweetDuck.Browser.Notification {
 
 		private readonly CefByteArrayResourceHandler resourceHandler = new CefByteArrayResourceHandler();
 
-		private DesktopNotification currentNotification;
+		private DesktopNotification? currentNotification;
 		private readonly HashSet<NotificationPauseReason> pauseReasons = new HashSet<NotificationPauseReason>();
 
-		public string CurrentTweetUrl => currentNotification?.TweetUrl;
+		public string? CurrentTweetUrl => currentNotification?.TweetUrl;
-		public string CurrentQuoteUrl => currentNotification?.QuoteUrl;
+		public string? CurrentQuoteUrl => currentNotification?.QuoteUrl;
 
 		protected bool IsPaused => pauseReasons.Count > 0;
 		protected internal bool IsCursorOverBrowser => browser.Bounds.Contains(PointToClient(Cursor.Position));
@@ -156,7 +156,7 @@ namespace TweetDuck.Browser.Notification {
 
 		// event handlers
 
-		private void owner_FormClosed(object sender, FormClosedEventArgs e) {
+		private void owner_FormClosed(object? sender, FormClosedEventArgs e) {
 			Close();
 		}
 
@@ -195,7 +195,7 @@ namespace TweetDuck.Browser.Notification {
 		}
 
 		protected virtual void UpdateTitle() {
-			string title = currentNotification?.ColumnTitle;
+			string? title = currentNotification?.ColumnTitle;
 			Text = string.IsNullOrEmpty(title) || !Config.DisplayNotificationColumn ? Program.BrandName : $"{Program.BrandName} - {title}";
 		}
 
@@ -214,7 +214,7 @@ namespace TweetDuck.Browser.Notification {
 			}
 		}
 
-		public void DisplayTooltip(string text) {
+		public void DisplayTooltip(string? text) {
 			if (string.IsNullOrEmpty(text)) {
 				toolTip.Hide(this);
 			}

windows/TweetDuck/Browser/Notification/FormNotificationExample.cs

@@ -32,7 +32,7 @@ namespace TweetDuck.Browser.Notification {
 			}
 		}
 
-		public event EventHandler Ready;
+		public event EventHandler? Ready;
 
 		private readonly DesktopNotification exampleNotification;
 

windows/TweetDuck/Browser/Notification/FormNotificationMain.cs

@@ -23,7 +23,7 @@ namespace TweetDuck.Browser.Notification {
 				this.notification = notification;
 			}
 
-			public void DisplayTooltip(string text) {
+			public void DisplayTooltip(string? text) {
 				notification.InvokeAsyncSafe(() => notification.DisplayTooltip(text));
 			}
 
@@ -175,14 +175,14 @@ namespace TweetDuck.Browser.Notification {
 
 		// event handlers
 
-		private void FormNotification_FormClosing(object sender, FormClosingEventArgs e) {
+		private void FormNotification_FormClosing(object? sender, FormClosingEventArgs e) {
 			if (e.CloseReason == CloseReason.UserClosing) {
 				HideNotification();
 				e.Cancel = true;
 			}
 		}
 
-		private void Browser_LoadingStateChanged(object sender, LoadingStateChangedEventArgs e) {
+		private void Browser_LoadingStateChanged(object? sender, LoadingStateChangedEventArgs e) {
 			if (!e.IsLoading && browser.Address != NotificationBrowser.BlankURL) {
 				this.InvokeSafe(() => {
 					Visible = true; // ensures repaint before moving the window to a visible location
@@ -191,12 +191,12 @@ namespace TweetDuck.Browser.Notification {
 			}
 		}
 
-		private void timerDisplayDelay_Tick(object sender, EventArgs e) {
+		private void timerDisplayDelay_Tick(object? sender, EventArgs e) {
 			OnNotificationReady();
 			timerDisplayDelay.Stop();
 		}
 
-		private void timerHideProgress_Tick(object sender, EventArgs e) {
+		private void timerHideProgress_Tick(object? sender, EventArgs e) {
 			bool isCursorInside = Bounds.Contains(Cursor.Position);
 
 			if (isCursorInside) {

windows/TweetDuck/Browser/Notification/FormNotificationTweet.cs

@@ -53,7 +53,7 @@ namespace TweetDuck.Browser.Notification {
 			}
 		}
 
-		private void WindowsSessionManager_LockStateChanged(object sender, EventArgs e) {
+		private void WindowsSessionManager_LockStateChanged(object? sender, EventArgs e) {
 			if (WindowsSessionManager.IsLocked) {
 				PauseNotification(NotificationPauseReason.WindowsSessionLocked);
 			}
@@ -78,7 +78,7 @@ namespace TweetDuck.Browser.Notification {
 
 		// event handlers
 
-		private void Config_MuteToggled(object sender, EventArgs e) {
+		private void Config_MuteToggled(object? sender, EventArgs e) {
 			if (Config.MuteNotifications) {
 				PauseNotification(NotificationPauseReason.UserConfiguration);
 			}
@@ -87,14 +87,14 @@ namespace TweetDuck.Browser.Notification {
 			}
 		}
 
-		private void timerCursorCheck_Tick(object sender, EventArgs e) {
+		private void timerCursorCheck_Tick(object? sender, EventArgs e) {
 			if (!IsCursorOverNotificationArea) {
 				ResumeNotification(NotificationPauseReason.CursorOverNotificationArea);
 				timerCursorCheck.Stop();
 			}
 		}
 
-		private void timerIdlePauseCheck_Tick(object sender, EventArgs e) {
+		private void timerIdlePauseCheck_Tick(object? sender, EventArgs e) {
 			if (NativeMethods.GetIdleSeconds() < Config.NotificationIdlePauseSeconds) {
 				ResumeNotification(NotificationPauseReason.SystemIdle);
 				timerIdlePauseCheck.Stop();

windows/TweetDuck/Browser/Notification/Screenshot/FormNotificationScreenshotable.cs

@@ -28,7 +28,7 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 			browserComponent.AttachBridgeObject("$TD_NotificationScreenshot", new ScreenshotBridge(this, SetScreenshotHeight, callback));
 
 			browserComponent.BrowserLoaded += (sender, args) => {
-				string script = ResourceUtils.ReadFileOrNull("notification/screenshot/screenshot.js");
+				string? script = ResourceUtils.ReadFileOrNull("notification/screenshot/screenshot.js");
 
 				if (script == null) {
 					this.InvokeAsyncSafe(callback);
@@ -47,29 +47,27 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 			this.height = BrowserUtils.Scale(browserHeight, SizeScale);
 		}
 
-		public Task<Image> TakeScreenshot(bool ignoreHeightError = false) {
+		public Task<Image>? TakeScreenshot() {
-			if (!ignoreHeightError) {
+			if (height == 0) {
-				if (height == 0) {
+				FormMessage.Error("Screenshot Failed", "Could not detect screenshot size.", FormMessage.OK);
-					FormMessage.Error("Screenshot Failed", "Could not detect screenshot size.", FormMessage.OK);
+				return null;
-					return null;
+			}
-				}
+			else if (height > ClientSize.Height) {
-				else if (height > ClientSize.Height) {
+				FormMessage.Error("Screenshot Failed", $"Screenshot is too large: {height}px > {ClientSize.Height}px", FormMessage.OK);
-					FormMessage.Error("Screenshot Failed", $"Screenshot is too large: {height}px > {ClientSize.Height}px", FormMessage.OK);
+				return null;
-					return null;
-				}
 			}
 
 			return Task.Run(TakeScreenshotImpl);
 		}
 
 		private async Task<Image> TakeScreenshotImpl() {
-			if (this.height == 0) {
+			if (height == 0) {
-				return null;
+				throw new InvalidOperationException("Screenshot height must not be zero!");
 			}
 
 			Viewport viewport = new Viewport {
-				Width = this.ClientSize.Width,
+				Width = ClientSize.Width,
-				Height = this.height,
+				Height = height,
 				Scale = 1
 			};
 

windows/TweetDuck/Browser/Notification/Screenshot/TweetScreenshotManager.cs

@@ -35,7 +35,7 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 		public const int WaitFrames = 5;
 		#endif
 
-		private FormNotificationScreenshotable screenshot;
+		private FormNotificationScreenshotable? screenshot;
 
 		public TweetScreenshotManager(FormBrowser owner, PluginManager pluginManager) {
 			this.owner = owner;
@@ -53,14 +53,14 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 			#endif
 		}
 
-		private void timeout_Tick(object sender, EventArgs e) {
+		private void timeout_Tick(object? sender, EventArgs e) {
 			timeout.Stop();
 			OnFinished();
 		}
 
-		private void disposer_Tick(object sender, EventArgs e) {
+		private void disposer_Tick(object? sender, EventArgs e) {
 			disposer.Stop();
-			screenshot.Dispose();
+			screenshot?.Dispose();
 			screenshot = null;
 		}
 
@@ -88,12 +88,12 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 			}
 
 			timeout.Stop();
-			screenshot.TakeScreenshot().ContinueWith(HandleResult, TaskScheduler.FromCurrentSynchronizationContext());
+			screenshot?.TakeScreenshot()?.ContinueWith(HandleResult, TaskScheduler.FromCurrentSynchronizationContext());
 		}
 
 		private void HandleResult(Task<Image> task) {
 			if (task.IsFaulted) {
-				App.ErrorHandler.HandleException("Screenshot Failed", "An error occurred while taking a screenshot.", true, task.Exception!.InnerException);
+				App.ErrorHandler.HandleException("Screenshot Failed", "An error occurred while taking a screenshot.", true, task.Exception!.InnerException!);
 			}
 			else if (task.IsCompleted) {
 				Clipboard.SetImage(task.Result);
@@ -111,7 +111,10 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 			debugger.Stop();
 			#endif
 
-			screenshot.Location = ControlExtensions.InvisibleLocation;
+			if (screenshot != null) {
+				screenshot.Location = ControlExtensions.InvisibleLocation;
+			}
+
 			owner.IsWaiting = false;
 			disposer.Start();
 		}
@@ -141,7 +144,7 @@ namespace TweetDuck.Browser.Notification.Screenshot {
 			debugger.Start();
 		}
 
-		private void debugger_Tick(object sender, EventArgs e) {
+		private void debugger_Tick(object? sender, EventArgs e) {
 			if (frameCounter < 63) {
 				int frame = ++frameCounter;
 				screenshot.TakeScreenshot(true).ContinueWith(task => SaveDebugFrame(task, frame), TaskScheduler.FromCurrentSynchronizationContext());

windows/TweetDuck/Browser/Notification/SoundNotification.cs

@@ -40,13 +40,13 @@ namespace TweetDuck.Browser.Notification {
 				".mp3"  => "audio/mp3",
 				".flac" => "audio/flac",
 				".opus" => "audio/ogg; codecs=opus",
-				_       => null
+				_       => "application/octet-stream"
 			};
 
 			try {
 				return (File.ReadAllBytes(path), mimeType);
 			} catch {
-				FormBrowser browser = FormManager.TryFind<FormBrowser>();
+				FormBrowser? browser = FormManager.TryFind<FormBrowser>();
 
 				browser?.InvokeAsyncSafe(() => {
 					using FormMessage form = new FormMessage("Sound Notification Error", "Could not find custom notification sound file:\n" + path, MessageBoxIcon.Error);

windows/TweetDuck/Browser/TrayIcon.cs

@@ -17,8 +17,8 @@ namespace TweetDuck.Browser {
 
 		private static UserConfig Config => Program.Config.User;
 
-		public event EventHandler ClickRestore;
+		public event EventHandler? ClickRestore;
-		public event EventHandler ClickClose;
+		public event EventHandler? ClickClose;
 
 		public bool Visible {
 			get {
@@ -85,30 +85,30 @@ namespace TweetDuck.Browser {
 
 		// event handlers
 
-		private void Config_MuteToggled(object sender, EventArgs e) {
+		private void Config_MuteToggled(object? sender, EventArgs e) {
 			UpdateIcon();
 		}
 
-		private void trayIcon_MouseClick(object sender, MouseEventArgs e) {
+		private void trayIcon_MouseClick(object? sender, MouseEventArgs e) {
 			if (e.Button == MouseButtons.Left) {
 				menuItemRestore_Click(sender, e);
 			}
 		}
 
-		private void contextMenu_Popup(object sender, EventArgs e) {
+		private void contextMenu_Popup(object? sender, EventArgs e) {
 			((ToolStripMenuItem) contextMenu.Items[1]).Checked = Config.MuteNotifications;
 		}
 
-		private void menuItemRestore_Click(object sender, EventArgs e) {
+		private void menuItemRestore_Click(object? sender, EventArgs e) {
 			ClickRestore?.Invoke(this, e);
 		}
 
-		private void menuItemMuteNotifications_Click(object sender, EventArgs e) {
+		private void menuItemMuteNotifications_Click(object? sender, EventArgs e) {
 			Config.MuteNotifications = !((ToolStripMenuItem) contextMenu.Items[1]).Checked;
 			Config.Save();
 		}
 
-		private void menuItemClose_Click(object sender, EventArgs e) {
+		private void menuItemClose_Click(object? sender, EventArgs e) {
 			ClickClose?.Invoke(this, e);
 		}
 	}

windows/TweetDuck/Configuration/Arguments.cs

@@ -21,7 +21,7 @@ namespace TweetDuck.Configuration {
 			return Current.HasFlag(flag);
 		}
 
-		public static string GetValue(string key) {
+		public static string? GetValue(string key) {
 			return Current.GetValue(key);
 		}
 

windows/TweetDuck/Configuration/UserConfig.cs

@@ -29,18 +29,18 @@ namespace TweetDuck.Configuration {
 		public bool EnableAnimatedImages      { get; set; } = true;
 		public bool HideTweetsByNftUsers      { get; set; } = false;
 
-		private bool _enableSmoothScrolling = true;
+		private bool _enableSmoothScrolling  = true;
-		private string _customCefArgs       = null;
+		private string? _customCefArgs       = null;
 
-		public string BrowserPath            { get; set; } = null;
+		public string? BrowserPath           { get; set; } = null;
-		public string BrowserPathArgs        { get; set; } = null;
+		public string? BrowserPathArgs       { get; set; } = null;
 		public bool IgnoreTrackingUrlWarning { get; set; } = false;
-		public string SearchEngineUrl        { get; set; } = null;
+		public string? SearchEngineUrl       { get; set; } = null;
 		private int _zoomLevel                             = 100;
 
-		public string VideoPlayerPath     { get; set; } = null;
+		public string? VideoPlayerPath     { get; set; } = null;
-		public string VideoPlayerPathArgs { get; set; } = null;
+		public string? VideoPlayerPathArgs { get; set; } = null;
-		public int VideoPlayerVolume      { get; set; } = 50;
+		public int VideoPlayerVolume       { get; set; } = 50;
 
 		public bool EnableSpellCheck { get; set; } = false;
 		private string _spellCheckLanguage         = "en-US";
@@ -51,8 +51,8 @@ namespace TweetDuck.Configuration {
 		private TrayIcon.Behavior _trayBehavior       = TrayIcon.Behavior.Disabled;
 		public bool EnableTrayHighlight { get; set; } = true;
 
-		public bool EnableUpdateCheck { get; set; } = true;
+		public bool EnableUpdateCheck  { get; set; } = true;
-		public string DismissedUpdate { get; set; } = null;
+		public string? DismissedUpdate { get; set; } = null;
 
 		public bool DisplayNotificationColumn    { get; set; } = false;
 		public bool NotificationMediaPreviews    { get; set; } = true;
@@ -74,13 +74,13 @@ namespace TweetDuck.Configuration {
 		public Size CustomNotificationSize               { get; set; } = Size.Empty;
 		public int NotificationScrollSpeed               { get; set; } = 100;
 
-		private string _notificationSoundPath;
+		private string? _notificationSoundPath;
 		private int _notificationSoundVolume = 100;
 
 		private bool _muteNotifications;
 
-		public string CustomBrowserCSS      { get; set; } = null;
+		public string? CustomBrowserCSS      { get; set; } = null;
-		public string CustomNotificationCSS { get; set; } = null;
+		public string? CustomNotificationCSS { get; set; } = null;
 
 		public bool DevToolsInContextMenu { get; set; } = false;
 		public bool DevToolsWindowOnTop   { get; set; } = true;
@@ -123,7 +123,7 @@ namespace TweetDuck.Configuration {
 			set => UpdatePropertyWithCallback(ref _enableSmoothScrolling, value, App.ConfigManager.TriggerProgramRestartRequested);
 		}
 
-		public string CustomCefArgs {
+		public string? CustomCefArgs {
 			get => _customCefArgs;
 			set => UpdatePropertyWithCallback(ref _customCefArgs, value, App.ConfigManager.TriggerProgramRestartRequested);
 		}
@@ -149,11 +149,11 @@ namespace TweetDuck.Configuration {
 
 		// EVENTS
 
-		public event EventHandler MuteToggled;
+		public event EventHandler? MuteToggled;
-		public event EventHandler ZoomLevelChanged;
+		public event EventHandler? ZoomLevelChanged;
-		public event EventHandler TrayBehaviorChanged;
+		public event EventHandler? TrayBehaviorChanged;
-		public event EventHandler SoundNotificationChanged;
+		public event EventHandler? SoundNotificationChanged;
-		public event EventHandler OptionsDialogClosed;
+		public event EventHandler? OptionsDialogClosed;
 
 		public void TriggerOptionsDialogClosed() {
 			OptionsDialogClosed?.Invoke(this, EventArgs.Empty);

windows/TweetDuck/Controls/ControlExtensions.cs

@@ -74,8 +74,8 @@ namespace TweetDuck.Controls {
 
 		public static void EnableMultilineShortcuts(this TextBox textBox) {
 			textBox.KeyDown += (sender, args) => {
-				if (args.Control && args.KeyCode == Keys.A) {
+				if (args.Control && args.KeyCode == Keys.A && sender is TextBox tb) {
-					((TextBox) sender).SelectAll();
+					tb.SelectAll();
 					args.SuppressKeyPress = true;
 					args.Handled = true;
 				}

windows/TweetDuck/Controls/FlatButton.cs

@@ -9,7 +9,7 @@ namespace TweetDuck.Controls {
 			GotFocus += FlatButton_GotFocus;
 		}
 
-		private void FlatButton_GotFocus(object sender, EventArgs e) { // removes extra border when focused
+		private void FlatButton_GotFocus(object? sender, EventArgs e) { // removes extra border when focused
 			NotifyDefault(false);
 		}
 	}

windows/TweetDuck/Controls/NumericUpDownEx.cs

@@ -3,7 +3,7 @@ using System.Windows.Forms;
 
 namespace TweetDuck.Controls {
 	sealed class NumericUpDownEx : NumericUpDown {
-		public string TextSuffix { get; set ; }
+		public string? TextSuffix { get; set; }
 
 		protected override void UpdateEditText() {
 			base.UpdateEditText();

windows/TweetDuck/Dialogs/FormAbout.cs

@@ -27,15 +27,15 @@ namespace TweetDuck.Dialogs {
 			}
 		}
 
-		private void OnLinkClicked(object sender, LinkLabelLinkClickedEventArgs e) {
+		private void OnLinkClicked(object? sender, LinkLabelLinkClickedEventArgs e) {
 			App.SystemHandler.OpenBrowser(e.Link.LinkData as string);
 		}
 
-		private void FormAbout_HelpRequested(object sender, HelpEventArgs hlpevent) {
+		private void FormAbout_HelpRequested(object? sender, HelpEventArgs hlpevent) {
 			ShowGuide();
 		}
 
-		private void FormAbout_HelpButtonClicked(object sender, CancelEventArgs e) {
+		private void FormAbout_HelpButtonClicked(object? sender, CancelEventArgs e) {
 			e.Cancel = true;
 			ShowGuide();
 		}

windows/TweetDuck/Dialogs/FormGuide.cs

@@ -12,12 +12,12 @@ namespace TweetDuck.Dialogs {
 	sealed partial class FormGuide : Form, FormManager.IAppDialog {
 		private const string GuideUrl = "td://guide/index.html";
 
-		public static void Show(string hash = null) {
+		public static void Show(string? hash = null) {
 			string url = GuideUrl + (string.IsNullOrEmpty(hash) ? string.Empty : "#" + hash);
-			FormGuide guide = FormManager.TryFind<FormGuide>();
+			FormGuide? guide = FormManager.TryFind<FormGuide>();
 
 			if (guide == null) {
-				FormBrowser owner = FormManager.TryFind<FormBrowser>();
+				FormBrowser? owner = FormManager.TryFind<FormBrowser>();
 
 				if (owner != null) {
 					new FormGuide(url, owner).Show(owner);

windows/TweetDuck/Dialogs/FormMessage.cs

@@ -22,23 +22,23 @@ namespace TweetDuck.Dialogs {
 		public const string Ignore = "Ignore";
 		public const string Exit = "Exit";
 
-		public static bool Information(string caption, string text, string buttonAccept, string buttonCancel = null) {
+		public static bool Information(string caption, string text, string buttonAccept, string? buttonCancel = null) {
 			return Show(caption, text, MessageBoxIcon.Information, buttonAccept, buttonCancel);
 		}
 
-		public static bool Warning(string caption, string text, string buttonAccept, string buttonCancel = null) {
+		public static bool Warning(string caption, string text, string buttonAccept, string? buttonCancel = null) {
 			return Show(caption, text, MessageBoxIcon.Warning, buttonAccept, buttonCancel);
 		}
 
-		public static bool Error(string caption, string text, string buttonAccept, string buttonCancel = null) {
+		public static bool Error(string caption, string text, string buttonAccept, string? buttonCancel = null) {
 			return Show(caption, text, MessageBoxIcon.Error, buttonAccept, buttonCancel);
 		}
 
-		public static bool Question(string caption, string text, string buttonAccept, string buttonCancel = null) {
+		public static bool Question(string caption, string text, string buttonAccept, string? buttonCancel = null) {
 			return Show(caption, text, MessageBoxIcon.Question, buttonAccept, buttonCancel);
 		}
 
-		public static bool Show(string caption, string text, MessageBoxIcon icon, string buttonAccept, string buttonCancel = null) {
+		public static bool Show(string caption, string text, MessageBoxIcon icon, string buttonAccept, string? buttonCancel = null) {
 			using FormMessage message = new FormMessage(caption, text, icon);
 
 			if (buttonCancel == null) {
@@ -54,7 +54,7 @@ namespace TweetDuck.Dialogs {
 
 		// Instance
 
-		public Button ClickedButton { get; private set; }
+		public Button? ClickedButton { get; private set; }
 
 		public bool HasIcon => icon != null;
 		public int ActionPanelY => panelActions.Location.Y;
@@ -68,7 +68,7 @@ namespace TweetDuck.Dialogs {
 			get => BrowserUtils.Scale(96, dpiScale);
 		}
 
-		private readonly Icon icon;
+		private readonly Icon? icon;
 		private readonly bool isReady;
 		private readonly float dpiScale;
 
@@ -115,7 +115,7 @@ namespace TweetDuck.Dialogs {
 			this.labelMessage.Text = text.Replace("\r", "").Replace("\n", Environment.NewLine);
 		}
 
-		private void FormMessage_SizeChanged(object sender, EventArgs e) {
+		private void FormMessage_SizeChanged(object? sender, EventArgs e) {
 			RecalculateButtonLocation();
 		}
 
@@ -135,7 +135,7 @@ namespace TweetDuck.Dialogs {
 			};
 
 			button.Click += (sender, args) => {
-				ClickedButton = (Button) sender;
+				ClickedButton = button;
 				DialogResult = result;
 				Close();
 			};
@@ -181,7 +181,7 @@ namespace TweetDuck.Dialogs {
 			}
 		}
 
-		private void labelMessage_SizeChanged(object sender, EventArgs e) {
+		private void labelMessage_SizeChanged(object? sender, EventArgs e) {
 			if (!isReady) {
 				return;
 			}

windows/TweetDuck/Dialogs/FormPlugins.cs

@@ -16,11 +16,12 @@ namespace TweetDuck.Dialogs {
 
 		private readonly PluginManager pluginManager;
 
+		#pragma warning disable CS8618
 		private FormPlugins() {
 			InitializeComponent();
-
 			Text = Program.BrandName + " Plugins";
 		}
+		#pragma warning restore CS8618
 
 		public FormPlugins(PluginManager pluginManager) : this() {
 			this.pluginManager = pluginManager;
@@ -68,7 +69,7 @@ namespace TweetDuck.Dialogs {
 			timerLayout.Start();
 		}
 
-		private void timerLayout_Tick(object sender, EventArgs e) {
+		private void timerLayout_Tick(object? sender, EventArgs e) {
 			timerLayout.Stop();
 
 			// stupid WinForms scrollbars and panels
@@ -76,8 +77,8 @@ namespace TweetDuck.Dialogs {
 			Padding = new Padding(Padding.Left, Padding.Top, Padding.Right - 1, Padding.Bottom - 1);
 		}
 
-		private void flowLayoutPlugins_Resize(object sender, EventArgs e) {
+		private void flowLayoutPlugins_Resize(object? sender, EventArgs e) {
-			Control lastPlugin = flowLayoutPlugins.Controls.OfType<PluginControl>().LastOrDefault();
+			Control? lastPlugin = flowLayoutPlugins.Controls.OfType<PluginControl>().LastOrDefault();
 
 			if (lastPlugin == null) {
 				return;
@@ -93,22 +94,22 @@ namespace TweetDuck.Dialogs {
 				control.Width = flowLayoutPlugins.Width - control.Margin.Horizontal - horizontalOffset;
 			}
 
-			flowLayoutPlugins.Controls[flowLayoutPlugins.Controls.Count - 1].Visible = !showScrollBar;
+			flowLayoutPlugins.Controls[^1].Visible = !showScrollBar;
 			flowLayoutPlugins.Focus();
 		}
 
-		private void btnOpenFolder_Click(object sender, EventArgs e) {
+		private void btnOpenFolder_Click(object? sender, EventArgs e) {
 			App.SystemHandler.OpenFileExplorer(pluginManager.GetPluginFolder(PluginGroup.Custom));
 		}
 
-		private void btnReload_Click(object sender, EventArgs e) {
+		private void btnReload_Click(object? sender, EventArgs e) {
 			if (FormMessage.Warning("Reloading Plugins", "This will also reload the browser window. Do you want to proceed?", FormMessage.Yes, FormMessage.No)) {
 				pluginManager.Reload();
 				ReloadPluginList();
 			}
 		}
 
-		private void btnClose_Click(object sender, EventArgs e) {
+		private void btnClose_Click(object? sender, EventArgs e) {
 			Close();
 		}
 	}

windows/TweetDuck/Dialogs/FormSettings.cs

@@ -25,9 +25,9 @@ namespace TweetDuck.Dialogs {
 		private readonly int buttonHeight;
 
 		private readonly Dictionary<Type, SettingsTab> tabs = new Dictionary<Type, SettingsTab>(8);
-		private SettingsTab currentTab;
+		private SettingsTab? currentTab;
 
-		public FormSettings(FormBrowser browser, PluginManager plugins, UpdateChecker updates, TweetDeckFunctions tweetDeckFunctions, Type startTab) {
+		public FormSettings(FormBrowser browser, PluginManager plugins, UpdateChecker updates, TweetDeckFunctions tweetDeckFunctions, Type? startTab) {
 			InitializeComponent();
 
 			Text = Program.BrandName + " Options";
@@ -56,19 +56,19 @@ namespace TweetDuck.Dialogs {
 		}
 
 		private void PrepareUnload() { // TODO refactor this further later
-			currentTab.Control.OnClosing();
+			currentTab?.Control.OnClosing();
 
 			App.ConfigManager.ProgramRestartRequested -= Config_ProgramRestartRequested;
 			App.ConfigManager.SaveAll();
 		}
 
-		private void Config_ProgramRestartRequested(object sender, EventArgs e) {
+		private void Config_ProgramRestartRequested(object? sender, EventArgs e) {
 			if (FormMessage.Information("TweetDuck Options", "The application must restart for the option to take place. Do you want to restart now?", FormMessage.Yes, FormMessage.No)) {
 				Program.Restart();
 			}
 		}
 
-		private void FormSettings_FormClosing(object sender, FormClosingEventArgs e) {
+		private void FormSettings_FormClosing(object? sender, FormClosingEventArgs e) {
 			PrepareUnload();
 
 			foreach (SettingsTab tab in tabs.Values) {
@@ -80,7 +80,7 @@ namespace TweetDuck.Dialogs {
 			browser.ResumeNotification(NotificationPauseReason.SettingsDialogOpen);
 		}
 
-		private void btnManageOptions_Click(object sender, EventArgs e) {
+		private void btnManageOptions_Click(object? sender, EventArgs e) {
 			PrepareUnload();
 
 			using DialogSettingsManage dialog = new DialogSettingsManage(plugins);
@@ -104,7 +104,7 @@ namespace TweetDuck.Dialogs {
 			}
 		}
 
-		private void btnClose_Click(object sender, EventArgs e) {
+		private void btnClose_Click(object? sender, EventArgs e) {
 			Close();
 		}
 
@@ -128,7 +128,7 @@ namespace TweetDuck.Dialogs {
 
 			panelButtons.Controls.Add(new Panel {
 				BackColor = Color.DimGray,
-				Location = new Point(0, panelButtons.Controls[panelButtons.Controls.Count - 1].Location.Y + buttonHeight),
+				Location = new Point(0, panelButtons.Controls[^1].Location.Y + buttonHeight),
 				Margin = new Padding(0),
 				Size = new Size(panelButtons.Width, 1)
 			});
@@ -182,7 +182,7 @@ namespace TweetDuck.Dialogs {
 			currentTab = tab;
 		}
 
-		private void control_MouseLeave(object sender, EventArgs e) {
+		private void control_MouseLeave(object? sender, EventArgs e) {
 			if (sender is ComboBox { DroppedDown: true } ) {
 				return; // prevents comboboxes from closing when MouseLeave event triggers during opening animation
 			}
@@ -190,7 +190,7 @@ namespace TweetDuck.Dialogs {
 			panelContents.Focus();
 		}
 
-		private void control_MouseWheel(object sender, MouseEventArgs e) {
+		private void control_MouseWheel(object? sender, MouseEventArgs e) {
 			((HandledMouseEventArgs) e).Handled = true;
 			panelContents.Focus();
 		}
@@ -202,7 +202,7 @@ namespace TweetDuck.Dialogs {
 			public bool IsInitialized => control != null;
 
 			private readonly Func<BaseTab> constructor;
-			private BaseTab control;
+			private BaseTab? control;
 
 			public SettingsTab(Button button, Func<BaseTab> constructor) {
 				this.Button = button;

windows/TweetDuck/Dialogs/Settings/DialogSettingsCSS.cs

@@ -12,7 +12,7 @@ namespace TweetDuck.Dialogs.Settings {
 		private readonly Action<string> reinjectBrowserCSS;
 		private readonly Action openDevTools;
 
-		public DialogSettingsCSS(string browserCSS, string notificationCSS, Action<string> reinjectBrowserCSS, Action openDevTools) {
+		public DialogSettingsCSS(string? browserCSS, string? notificationCSS, Action<string> reinjectBrowserCSS, Action openDevTools) {
 			InitializeComponent();
 
 			Text = Program.BrandName + " Options - CSS";
@@ -30,8 +30,8 @@ namespace TweetDuck.Dialogs.Settings {
 			textBoxBrowserCSS.Select(textBoxBrowserCSS.TextLength, 0);
 		}
 
-		private void tabPanel_SelectedIndexChanged(object sender, EventArgs e) {
+		private void tabPanel_SelectedIndexChanged(object? sender, EventArgs e) {
-			TextBox tb = tabPanel.SelectedTab.Controls.OfType<TextBox>().FirstOrDefault();
+			TextBox? tb = tabPanel.SelectedTab.Controls.OfType<TextBox>().FirstOrDefault();
 
 			if (tb != null) {
 				tb.Focus();
@@ -39,8 +39,8 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void textBoxCSS_KeyDown(object sender, KeyEventArgs e) {
+		private void textBoxCSS_KeyDown(object? sender, KeyEventArgs e) {
-			TextBox tb = (TextBox) sender;
+			TextBox tb = (TextBox) sender!;
 			string text = tb.Text;
 
 			if (e.KeyCode == Keys.Back && e.Modifiers == Keys.Control) {
@@ -79,7 +79,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 			else if (e.KeyCode == Keys.Enter && e.Modifiers == Keys.None && tb.SelectionLength == 0) {
 				int insertAt = tb.SelectionStart, cursorOffset = 0;
-				string insertText;
+				string? insertText;
 
 				if (insertAt == 0) {
 					return;
@@ -97,8 +97,9 @@ namespace TweetDuck.Dialogs.Settings {
 				}
 				else {
 					int lineStart = text.LastIndexOf('\n', tb.SelectionStart - 1);
-
+					var firstIndex = (lineStart == -1 ? 0 : lineStart + 1);
-					Match match = Regex.Match(text.Substring(lineStart == -1 ? 0 : lineStart + 1), "^([ \t]+)");
+					
+					Match match = Regex.Match(text[firstIndex..], "^([ \t]+)");
 					insertText = match.Success ? Environment.NewLine + match.Groups[1].Value : null;
 				}
 
@@ -110,26 +111,26 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void textBoxBrowserCSS_KeyUp(object sender, KeyEventArgs e) {
+		private void textBoxBrowserCSS_KeyUp(object? sender, KeyEventArgs e) {
 			timerTestBrowser.Stop();
 			timerTestBrowser.Start();
 		}
 
-		private void timerTestBrowser_Tick(object sender, EventArgs e) {
+		private void timerTestBrowser_Tick(object? sender, EventArgs e) {
 			reinjectBrowserCSS(textBoxBrowserCSS.Text);
 			timerTestBrowser.Stop();
 		}
 
-		private void btnOpenDevTools_Click(object sender, EventArgs e) {
+		private void btnOpenDevTools_Click(object? sender, EventArgs e) {
 			openDevTools();
 		}
 
-		private void btnApply_Click(object sender, EventArgs e) {
+		private void btnApply_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.OK;
 			Close();
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.Cancel;
 			Close();
 		}

windows/TweetDuck/Dialogs/Settings/DialogSettingsCefArgs.cs

@@ -10,7 +10,7 @@ namespace TweetDuck.Dialogs.Settings {
 
 		private readonly string initialArgs;
 
-		public DialogSettingsCefArgs(string args) {
+		public DialogSettingsCefArgs(string? args) {
 			InitializeComponent();
 
 			Text = Program.BrandName + " Options - CEF Arguments";
@@ -20,11 +20,11 @@ namespace TweetDuck.Dialogs.Settings {
 			textBoxArgs.Select(textBoxArgs.Text.Length, 0);
 		}
 
-		private void btnHelp_Click(object sender, EventArgs e) {
+		private void btnHelp_Click(object? sender, EventArgs e) {
 			App.SystemHandler.OpenBrowser("http://peter.sh/experiments/chromium-command-line-switches/");
 		}
 
-		private void btnApply_Click(object sender, EventArgs e) {
+		private void btnApply_Click(object? sender, EventArgs e) {
 			if (CefArgs == initialArgs) {
 				DialogResult = DialogResult.Cancel;
 				Close();
@@ -40,7 +40,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.Cancel;
 			Close();
 		}

windows/TweetDuck/Dialogs/Settings/DialogSettingsExternalProgram.cs

@@ -5,12 +5,12 @@ using IOPath = System.IO.Path;
 
 namespace TweetDuck.Dialogs.Settings {
 	sealed partial class DialogSettingsExternalProgram : Form {
-		public string Path {
+		public string? Path {
 			get => StringUtils.NullIfEmpty(textBoxPath.Text);
 			set => textBoxPath.Text = value ?? string.Empty;
 		}
 
-		public string Args {
+		public string? Args {
 			get => StringUtils.NullIfEmpty(textBoxArgs.Text);
 			set => textBoxArgs.Text = value ?? string.Empty;
 		}
@@ -27,7 +27,7 @@ namespace TweetDuck.Dialogs.Settings {
 			this.fileDialogTitle = fileDialogTitle;
 		}
 
-		private void btnBrowse_Click(object sender, EventArgs e) {
+		private void btnBrowse_Click(object? sender, EventArgs e) {
 			using OpenFileDialog dialog = new OpenFileDialog {
 				AutoUpgradeEnabled = true,
 				DereferenceLinks = true,
@@ -42,12 +42,12 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnApply_Click(object sender, EventArgs e) {
+		private void btnApply_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.OK;
 			Close();
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.Cancel;
 			Close();
 		}

windows/TweetDuck/Dialogs/Settings/DialogSettingsManage.cs

@@ -35,7 +35,7 @@ namespace TweetDuck.Dialogs.Settings {
 		private readonly bool openImportImmediately;
 
 		private State currentState;
-		private ProfileManager importManager;
+		private ProfileManager? importManager;
 		private bool requestedRestartFromConfig;
 
 		private ProfileManager.Items _selectedItems = ProfileManager.Items.None;
@@ -59,16 +59,16 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void radioDecision_CheckedChanged(object sender, EventArgs e) {
+		private void radioDecision_CheckedChanged(object? sender, EventArgs e) {
 			btnContinue.Enabled = true;
 		}
 
-		private void checkBoxSelection_CheckedChanged(object sender, EventArgs e) {
+		private void checkBoxSelection_CheckedChanged(object? sender, EventArgs e) {
-			CheckBox cb = (CheckBox) sender;
+			CheckBox cb = (CheckBox) sender!;
 			SetFlag(checkBoxMap[cb], cb.Checked);
 		}
 
-		private void btnContinue_Click(object sender, EventArgs e) {
+		private void btnContinue_Click(object? sender, EventArgs e) {
 			string file;
 
 			switch (currentState) {
@@ -167,7 +167,7 @@ namespace TweetDuck.Dialogs.Settings {
 					break;
 
 				case State.Import:
-					if (importManager.Import(SelectedItems)) {
+					if (importManager!.Import(SelectedItems)) {
 						App.ConfigManager.ProgramRestartRequested += Config_ProgramRestartRequested;
 						App.ConfigManager.ReloadAll();
 						App.ConfigManager.SaveAll();
@@ -209,12 +209,12 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.Cancel;
 			Close();
 		}
 
-		private void Config_ProgramRestartRequested(object sender, EventArgs e) {
+		private void Config_ProgramRestartRequested(object? sender, EventArgs e) {
 			requestedRestartFromConfig = true;
 		}
 

windows/TweetDuck/Dialogs/Settings/DialogSettingsRestart.cs

@@ -6,7 +6,7 @@ using TweetLib.Utils.Collections;
 
 namespace TweetDuck.Dialogs.Settings {
 	sealed partial class DialogSettingsRestart : Form {
-		public CommandLineArgs Args { get; private set; }
+		public CommandLineArgs Args { get; private set; } = null!;
 
 		public DialogSettingsRestart(CommandLineArgs currentArgs) {
 			InitializeComponent();
@@ -28,7 +28,7 @@ namespace TweetDuck.Dialogs.Settings {
 			Text = Program.BrandName + " Arguments";
 		}
 
-		private void control_Change(object sender, EventArgs e) {
+		private void control_Change(object? sender, EventArgs e) {
 			Args = new CommandLineArgs();
 
 			if (cbLogging.Checked) {
@@ -43,18 +43,18 @@ namespace TweetDuck.Dialogs.Settings {
 			tbShortcutTarget.Select(tbShortcutTarget.Text.Length, 0);
 		}
 
-		private void tbShortcutTarget_Click(object sender, EventArgs e) {
+		private void tbShortcutTarget_Click(object? sender, EventArgs e) {
 			if (tbShortcutTarget.SelectionLength == 0) {
 				tbShortcutTarget.SelectAll();
 			}
 		}
 
-		private void btnRestart_Click(object sender, EventArgs e) {
+		private void btnRestart_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.OK;
 			Close();
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.Cancel;
 			Close();
 		}

windows/TweetDuck/Dialogs/Settings/DialogSettingsSearchEngine.cs

@@ -14,12 +14,12 @@ namespace TweetDuck.Dialogs.Settings {
 			textBoxUrl.Select(textBoxUrl.Text.Length, 0);
 		}
 
-		private void btnApply_Click(object sender, EventArgs e) {
+		private void btnApply_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.OK;
 			Close();
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			DialogResult = DialogResult.Cancel;
 			Close();
 		}

windows/TweetDuck/Dialogs/Settings/TabSettingsAdvanced.cs

@@ -9,10 +9,10 @@ using TweetLib.Core;
 
 namespace TweetDuck.Dialogs.Settings {
 	sealed partial class TabSettingsAdvanced : FormSettings.BaseTab {
-		private readonly Action<string> reinjectBrowserCSS;
+		private readonly Action<string?> reinjectBrowserCSS;
 		private readonly Action openDevTools;
 
-		public TabSettingsAdvanced(Action<string> reinjectBrowserCSS, Action openDevTools) {
+		public TabSettingsAdvanced(Action<string?> reinjectBrowserCSS, Action openDevTools) {
 			InitializeComponent();
 
 			this.reinjectBrowserCSS = reinjectBrowserCSS;
@@ -98,19 +98,19 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Application
 
-		private void btnOpenAppFolder_Click(object sender, EventArgs e) {
+		private void btnOpenAppFolder_Click(object? sender, EventArgs e) {
 			App.SystemHandler.OpenFileExplorer(App.ProgramPath);
 		}
 
-		private void btnOpenDataFolder_Click(object sender, EventArgs e) {
+		private void btnOpenDataFolder_Click(object? sender, EventArgs e) {
 			App.SystemHandler.OpenFileExplorer(App.StoragePath);
 		}
 
-		private void btnRestart_Click(object sender, EventArgs e) {
+		private void btnRestart_Click(object? sender, EventArgs e) {
 			Program.Restart();
 		}
 
-		private void btnRestartArgs_Click(object sender, EventArgs e) {
+		private void btnRestartArgs_Click(object? sender, EventArgs e) {
 			using DialogSettingsRestart dialog = new DialogSettingsRestart(Arguments.GetCurrentClean());
 
 			if (dialog.ShowDialog() == DialogResult.OK) {
@@ -122,15 +122,15 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Browser Settings
 
-		private void checkTouchAdjustment_CheckedChanged(object sender, EventArgs e) {
+		private void checkTouchAdjustment_CheckedChanged(object? sender, EventArgs e) {
 			SysConfig.EnableTouchAdjustment = checkTouchAdjustment.Checked;
 		}
 
-		private void checkAutomaticallyDetectColorProfile_CheckedChanged(object sender, EventArgs e) {
+		private void checkAutomaticallyDetectColorProfile_CheckedChanged(object? sender, EventArgs e) {
 			SysConfig.EnableColorProfileDetection = checkAutomaticallyDetectColorProfile.Checked;
 		}
 
-		private void checkHardwareAcceleration_CheckedChanged(object sender, EventArgs e) {
+		private void checkHardwareAcceleration_CheckedChanged(object? sender, EventArgs e) {
 			SysConfig.HardwareAcceleration = checkHardwareAcceleration.Checked;
 		}
 
@@ -138,13 +138,13 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Browser Cache
 
-		private void btnClearCache_Click(object sender, EventArgs e) {
+		private void btnClearCache_Click(object? sender, EventArgs e) {
 			btnClearCache.Enabled = false;
 			BrowserCache.SetClearOnExit();
 			FormMessage.Information("Clear Cache", "Cache will be automatically cleared when TweetDuck exits.", FormMessage.OK);
 		}
 
-		private void checkClearCacheAuto_CheckedChanged(object sender, EventArgs e) {
+		private void checkClearCacheAuto_CheckedChanged(object? sender, EventArgs e) {
 			numClearCacheThreshold.Enabled = checkClearCacheAuto.Checked;
 		}
 
@@ -152,11 +152,12 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Configuration
 
-		private void btnEditCefArgs_Click(object sender, EventArgs e) {
+		private void btnEditCefArgs_Click(object? sender, EventArgs e) {
-			DialogSettingsCefArgs form = new DialogSettingsCefArgs(Config.CustomCefArgs);
+			var parentForm = ParentForm ?? throw new InvalidOperationException("Dialog does not have a parent form!");
+			var form = new DialogSettingsCefArgs(Config.CustomCefArgs);
 
 			form.VisibleChanged += (sender2, args2) => {
-				form.MoveToCenter(ParentForm);
+				form.MoveToCenter(parentForm);
 			};
 
 			form.FormClosed += (sender2, args2) => {
@@ -169,15 +170,16 @@ namespace TweetDuck.Dialogs.Settings {
 				form.Dispose();
 			};
 
-			form.Show(ParentForm);
+			form.Show(parentForm);
-			NativeMethods.SetFormDisabled(ParentForm, true);
+			NativeMethods.SetFormDisabled(parentForm, true);
 		}
 
-		private void btnEditCSS_Click(object sender, EventArgs e) {
+		private void btnEditCSS_Click(object? sender, EventArgs e) {
-			DialogSettingsCSS form = new DialogSettingsCSS(Config.CustomBrowserCSS, Config.CustomNotificationCSS, reinjectBrowserCSS, openDevTools);
+			var parentForm = ParentForm ?? throw new InvalidOperationException("Dialog does not have a parent form!");
+			var form = new DialogSettingsCSS(Config.CustomBrowserCSS, Config.CustomNotificationCSS, reinjectBrowserCSS, openDevTools);
 
 			form.VisibleChanged += (sender2, args2) => {
-				form.MoveToCenter(ParentForm);
+				form.MoveToCenter(parentForm);
 			};
 
 			form.FormClosed += (sender2, args2) => {
@@ -192,8 +194,8 @@ namespace TweetDuck.Dialogs.Settings {
 				form.Dispose();
 			};
 
-			form.Show(ParentForm);
+			form.Show(parentForm);
-			NativeMethods.SetFormDisabled(ParentForm, true);
+			NativeMethods.SetFormDisabled(parentForm, true);
 		}
 
 		private void RestoreParentForm() {
@@ -206,7 +208,7 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Proxy
 
-		private void checkUseSystemProxyForAllConnections_CheckedChanged(object sender, EventArgs e) {
+		private void checkUseSystemProxyForAllConnections_CheckedChanged(object? sender, EventArgs e) {
 			SysConfig.UseSystemProxyForAllConnections = checkUseSystemProxyForAllConnections.Checked;
 		}
 
@@ -214,11 +216,11 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Development Tools
 
-		private void checkDevToolsInContextMenuOnCheckedChanged(object sender, EventArgs e) {
+		private void checkDevToolsInContextMenuOnCheckedChanged(object? sender, EventArgs e) {
 			Config.DevToolsInContextMenu = checkDevToolsInContextMenu.Checked;
 		}
 
-		private void checkDevToolsWindowOnTop_CheckedChanged(object sender, EventArgs e) {
+		private void checkDevToolsWindowOnTop_CheckedChanged(object? sender, EventArgs e) {
 			Config.DevToolsWindowOnTop = checkDevToolsWindowOnTop.Checked;
 		}
 

windows/TweetDuck/Dialogs/Settings/TabSettingsFeedback.cs

@@ -13,7 +13,7 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Feedback
 
-		private void btnSendFeedback_Click(object sender, EventArgs e) {
+		private void btnSendFeedback_Click(object? sender, EventArgs e) {
 			App.SystemHandler.OpenBrowser(Lib.IssueTrackerUrl + "/new");
 		}
 

windows/TweetDuck/Dialogs/Settings/TabSettingsGeneral.cs

@@ -171,27 +171,27 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region User Interface
 
-		private void checkExpandLinks_CheckedChanged(object sender, EventArgs e) {
+		private void checkExpandLinks_CheckedChanged(object? sender, EventArgs e) {
 			Config.ExpandLinksOnHover = checkExpandLinks.Checked;
 		}
 
-		private void checkFocusDmInput_CheckedChanged(object sender, EventArgs e) {
+		private void checkFocusDmInput_CheckedChanged(object? sender, EventArgs e) {
 			Config.FocusDmInput = checkFocusDmInput.Checked;
 		}
 
-		private void checkOpenSearchInFirstColumn_CheckedChanged(object sender, EventArgs e) {
+		private void checkOpenSearchInFirstColumn_CheckedChanged(object? sender, EventArgs e) {
 			Config.OpenSearchInFirstColumn = checkOpenSearchInFirstColumn.Checked;
 		}
 
-		private void checkKeepLikeFollowDialogsOpen_CheckedChanged(object sender, EventArgs e) {
+		private void checkKeepLikeFollowDialogsOpen_CheckedChanged(object? sender, EventArgs e) {
 			Config.KeepLikeFollowDialogsOpen = checkKeepLikeFollowDialogsOpen.Checked;
 		}
 
-		private void checkSmoothScrolling_CheckedChanged(object sender, EventArgs e) {
+		private void checkSmoothScrolling_CheckedChanged(object? sender, EventArgs e) {
 			Config.EnableSmoothScrolling = checkSmoothScrolling.Checked;
 		}
 
-		private void trackBarZoom_ValueChanged(object sender, EventArgs e) {
+		private void trackBarZoom_ValueChanged(object? sender, EventArgs e) {
 			if (trackBarZoom.AlignValueToTick()) {
 				zoomUpdateTimer.Stop();
 				zoomUpdateTimer.Start();
@@ -199,7 +199,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void zoomUpdateTimer_Tick(object sender, EventArgs e) {
+		private void zoomUpdateTimer_Tick(object? sender, EventArgs e) {
 			Config.ZoomLevel = trackBarZoom.Value;
 			zoomUpdateTimer.Stop();
 		}
@@ -208,16 +208,16 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Twitter
 
-		private void checkBestImageQuality_CheckedChanged(object sender, EventArgs e) {
+		private void checkBestImageQuality_CheckedChanged(object? sender, EventArgs e) {
 			Config.BestImageQuality = checkBestImageQuality.Checked;
 		}
 
-		private void checkHideTweetsByNftUsers_CheckedChanged(object sender, EventArgs e) {
+		private void checkHideTweetsByNftUsers_CheckedChanged(object? sender, EventArgs e) {
 			Config.HideTweetsByNftUsers = checkHideTweetsByNftUsers.Checked;
 			BeginInvoke(reloadTweetDeck);
 		}
 
-		private void checkAnimatedAvatars_CheckedChanged(object sender, EventArgs e) {
+		private void checkAnimatedAvatars_CheckedChanged(object? sender, EventArgs e) {
 			Config.EnableAnimatedImages = checkAnimatedAvatars.Checked;
 			BrowserProcessHandler.UpdatePrefs().ContinueWith(task => reloadColumns());
 		}
@@ -226,18 +226,18 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Updates
 
-		private void checkUpdateNotifications_CheckedChanged(object sender, EventArgs e) {
+		private void checkUpdateNotifications_CheckedChanged(object? sender, EventArgs e) {
 			Config.EnableUpdateCheck = checkUpdateNotifications.Checked;
 		}
 
-		private void btnCheckUpdates_Click(object sender, EventArgs e) {
+		private void btnCheckUpdates_Click(object? sender, EventArgs e) {
 			Config.DismissedUpdate = null;
 
 			btnCheckUpdates.Enabled = false;
 			updateCheckEventId = updates.Check(true);
 		}
 
-		private void updates_CheckFinished(object sender, UpdateCheckEventArgs e) {
+		private void updates_CheckFinished(object? sender, UpdateCheckEventArgs e) {
 			if (e.EventId == updateCheckEventId) {
 				btnCheckUpdates.Enabled = true;
 
@@ -264,7 +264,7 @@ namespace TweetDuck.Dialogs.Settings {
 				comboBoxCustomBrowser.SelectedIndex = browserListIndexDefault;
 			}
 			else {
-				WindowsUtils.Browser browserInfo = comboBoxCustomBrowser.Items.OfType<WindowsUtils.Browser>().FirstOrDefault(browser => browser.Path == Config.BrowserPath);
+				WindowsUtils.Browser? browserInfo = comboBoxCustomBrowser.Items.OfType<WindowsUtils.Browser>().FirstOrDefault(browser => browser.Path == Config.BrowserPath);
 
 				if (browserInfo == null || Config.BrowserPathArgs != null) {
 					comboBoxCustomBrowser.SelectedIndex = browserListIndexCustom;
@@ -277,7 +277,7 @@ namespace TweetDuck.Dialogs.Settings {
 			UpdateBrowserChangeButton();
 		}
 
-		private void comboBoxCustomBrowser_SelectedIndexChanged(object sender, EventArgs e) {
+		private void comboBoxCustomBrowser_SelectedIndexChanged(object? sender, EventArgs e) {
 			if (comboBoxCustomBrowser.SelectedIndex == browserListIndexCustom) {
 				btnCustomBrowserChange_Click(sender, e);
 			}
@@ -288,7 +288,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnCustomBrowserChange_Click(object sender, EventArgs e) {
+		private void btnCustomBrowserChange_Click(object? sender, EventArgs e) {
 			using (DialogSettingsExternalProgram dialog = new DialogSettingsExternalProgram("External Browser", "Open Links With...") {
 				Path = Config.BrowserPath,
 				Args = Config.BrowserPathArgs
@@ -319,7 +319,7 @@ namespace TweetDuck.Dialogs.Settings {
 			UpdateVideoPlayerChangeButton();
 		}
 
-		private void comboBoxCustomVideoPlayer_SelectedIndexChanged(object sender, EventArgs e) {
+		private void comboBoxCustomVideoPlayer_SelectedIndexChanged(object? sender, EventArgs e) {
 			if (comboBoxCustomVideoPlayer.SelectedIndex == videoPlayerListIndexCustom) {
 				btnCustomVideoPlayerChange_Click(sender, e);
 			}
@@ -330,7 +330,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnCustomVideoPlayerChange_Click(object sender, EventArgs e) {
+		private void btnCustomVideoPlayerChange_Click(object? sender, EventArgs e) {
 			using (DialogSettingsExternalProgram dialog = new DialogSettingsExternalProgram("External Video Player", "Play Videos With...") {
 				Path = Config.VideoPlayerPath,
 				Args = Config.VideoPlayerPathArgs
@@ -346,7 +346,7 @@ namespace TweetDuck.Dialogs.Settings {
 			comboBoxCustomVideoPlayer.SelectedIndexChanged += comboBoxCustomVideoPlayer_SelectedIndexChanged;
 		}
 
-		private void comboBoxSearchEngine_SelectedIndexChanged(object sender, EventArgs e) {
+		private void comboBoxSearchEngine_SelectedIndexChanged(object? sender, EventArgs e) {
 			if (comboBoxSearchEngine.SelectedIndex == searchEngineIndexCustom) {
 				using (DialogSettingsSearchEngine dialog = new DialogSettingsSearchEngine()) {
 					if (dialog.ShowDialog() == DialogResult.OK) {
@@ -368,7 +368,7 @@ namespace TweetDuck.Dialogs.Settings {
 				comboBoxSearchEngine.SelectedIndex = searchEngineIndexDefault;
 			}
 			else {
-				SearchEngine engineInfo = comboBoxSearchEngine.Items.OfType<SearchEngine>().FirstOrDefault(engine => engine.Url == Config.SearchEngineUrl);
+				SearchEngine? engineInfo = comboBoxSearchEngine.Items.OfType<SearchEngine>().FirstOrDefault(engine => engine.Url == Config.SearchEngineUrl);
 
 				if (engineInfo == null) {
 					comboBoxSearchEngine.SelectedIndex = searchEngineIndexCustom;
@@ -389,7 +389,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 
 			public override int GetHashCode() => Name.GetHashCode();
-			public override bool Equals(object obj) => obj is SearchEngine other && Name == other.Name;
+			public override bool Equals(object? obj) => obj is SearchEngine other && Name == other.Name;
 			public override string ToString() => Name;
 		}
 
@@ -397,20 +397,20 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Locales
 
-		private void checkSpellCheck_CheckedChanged(object sender, EventArgs e) {
+		private void checkSpellCheck_CheckedChanged(object? sender, EventArgs e) {
 			Config.EnableSpellCheck = checkSpellCheck.Checked;
 			BrowserProcessHandler.UpdatePrefs();
 		}
 
-		private void comboBoxSpellCheckLanguage_SelectedValueChanged(object sender, EventArgs e) {
+		private void comboBoxSpellCheckLanguage_SelectedValueChanged(object? sender, EventArgs e) {
 			Config.SpellCheckLanguage = (comboBoxSpellCheckLanguage.SelectedItem as Language)?.Code ?? "en-US";
 		}
 
-		private void comboBoxTranslationTarget_SelectedValueChanged(object sender, EventArgs e) {
+		private void comboBoxTranslationTarget_SelectedValueChanged(object? sender, EventArgs e) {
 			Config.TranslationTarget = (comboBoxTranslationTarget.SelectedItem as Language)?.Code ?? "en";
 		}
 
-		private void comboBoxFirstDayOfWeek_SelectedValueChanged(object sender, EventArgs e) {
+		private void comboBoxFirstDayOfWeek_SelectedValueChanged(object? sender, EventArgs e) {
 			Config.CalendarFirstDay = (comboBoxFirstDayOfWeek.SelectedItem as DayOfWeekItem)?.Id ?? -1;
 		}
 
@@ -424,7 +424,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 
 			public override int GetHashCode() => Name.GetHashCode();
-			public override bool Equals(object obj) => obj is DayOfWeekItem other && Name == other.Name;
+			public override bool Equals(object? obj) => obj is DayOfWeekItem other && Name == other.Name;
 			public override string ToString() => Name;
 		}
 

windows/TweetDuck/Dialogs/Settings/TabSettingsNotifications.cs

@@ -143,7 +143,7 @@ namespace TweetDuck.Dialogs.Settings {
 			trackBarScrollSpeed.ValueChanged += trackBarScrollSpeed_ValueChanged;
 		}
 
-		private void TabSettingsNotifications_ParentChanged(object sender, EventArgs e) {
+		private void TabSettingsNotifications_ParentChanged(object? sender, EventArgs e) {
 			if (Parent == null) {
 				notification.HideNotification();
 			}
@@ -152,13 +152,13 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void notification_Move(object sender, EventArgs e) {
+		private void notification_Move(object? sender, EventArgs e) {
 			if (radioLocCustom.Checked && notification.Location != ControlExtensions.InvisibleLocation) {
 				Config.CustomNotificationPosition = notification.Location;
 			}
 		}
 
-		private void notification_ResizeEnd(object sender, EventArgs e) {
+		private void notification_ResizeEnd(object? sender, EventArgs e) {
 			if (radioSizeCustom.Checked) {
 				Config.CustomNotificationSize = notification.BrowserSize;
 				notification.ShowExampleNotification(false);
@@ -167,28 +167,28 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region General
 
-		private void checkColumnName_CheckedChanged(object sender, EventArgs e) {
+		private void checkColumnName_CheckedChanged(object? sender, EventArgs e) {
 			Config.DisplayNotificationColumn = checkColumnName.Checked;
 			notification.ShowExampleNotification(false);
 		}
 
-		private void checkMediaPreviews_CheckedChanged(object sender, EventArgs e) {
+		private void checkMediaPreviews_CheckedChanged(object? sender, EventArgs e) {
 			Config.NotificationMediaPreviews = checkMediaPreviews.Checked;
 		}
 
-		private void checkSkipOnLinkClick_CheckedChanged(object sender, EventArgs e) {
+		private void checkSkipOnLinkClick_CheckedChanged(object? sender, EventArgs e) {
 			Config.NotificationSkipOnLinkClick = checkSkipOnLinkClick.Checked;
 		}
 
-		private void checkNonIntrusive_CheckedChanged(object sender, EventArgs e) {
+		private void checkNonIntrusive_CheckedChanged(object? sender, EventArgs e) {
 			Config.NotificationNonIntrusiveMode = checkNonIntrusive.Checked;
 		}
 
-		private void comboBoxIdlePause_SelectedValueChanged(object sender, EventArgs e) {
+		private void comboBoxIdlePause_SelectedValueChanged(object? sender, EventArgs e) {
 			Config.NotificationIdlePauseSeconds = IdlePauseSeconds[comboBoxIdlePause.SelectedIndex];
 		}
 
-		private void trackBarOpacity_ValueChanged(object sender, EventArgs e) {
+		private void trackBarOpacity_ValueChanged(object? sender, EventArgs e) {
 			if (trackBarOpacity.AlignValueToTick()) {
 				Config.NotificationWindowOpacity = trackBarOpacity.Value;
 				labelOpacityValue.Text = Config.NotificationWindowOpacity + "%";
@@ -199,18 +199,18 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Timer
 
-		private void checkNotificationTimer_CheckedChanged(object sender, EventArgs e) {
+		private void checkNotificationTimer_CheckedChanged(object? sender, EventArgs e) {
 			Config.DisplayNotificationTimer = checkNotificationTimer.Checked;
 			checkTimerCountDown.Enabled = checkNotificationTimer.Checked;
 			notification.ShowExampleNotification(true);
 		}
 
-		private void checkTimerCountDown_CheckedChanged(object sender, EventArgs e) {
+		private void checkTimerCountDown_CheckedChanged(object? sender, EventArgs e) {
 			Config.NotificationTimerCountDown = checkTimerCountDown.Checked;
 			notification.ShowExampleNotification(true);
 		}
 
-		private void trackBarDuration_ValueChanged(object sender, EventArgs e) {
+		private void trackBarDuration_ValueChanged(object? sender, EventArgs e) {
 			durationUpdateTimer.Stop();
 			durationUpdateTimer.Start();
 
@@ -218,19 +218,19 @@ namespace TweetDuck.Dialogs.Settings {
 			labelDurationValue.Text = Config.NotificationDurationValue + " ms/c";
 		}
 
-		private void btnDurationShort_Click(object sender, EventArgs e) {
+		private void btnDurationShort_Click(object? sender, EventArgs e) {
 			trackBarDuration.Value = 15;
 		}
 
-		private void btnDurationMedium_Click(object sender, EventArgs e) {
+		private void btnDurationMedium_Click(object? sender, EventArgs e) {
 			trackBarDuration.Value = 25;
 		}
 
-		private void btnDurationLong_Click(object sender, EventArgs e) {
+		private void btnDurationLong_Click(object? sender, EventArgs e) {
 			trackBarDuration.Value = 35;
 		}
 
-		private void durationUpdateTimer_Tick(object sender, EventArgs e) {
+		private void durationUpdateTimer_Tick(object? sender, EventArgs e) {
 			notification.ShowExampleNotification(true);
 			durationUpdateTimer.Stop();
 		}
@@ -239,7 +239,7 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Location
 
-		private void radioLoc_CheckedChanged(object sender, EventArgs e) {
+		private void radioLoc_CheckedChanged(object? sender, EventArgs e) {
 			if (radioLocTL.Checked) {
 				Config.NotificationPosition = DesktopNotification.Position.TopLeft;
 			}
@@ -257,7 +257,7 @@ namespace TweetDuck.Dialogs.Settings {
 			notification.ShowExampleNotification(false);
 		}
 
-		private void radioLocCustom_Click(object sender, EventArgs e) {
+		private void radioLocCustom_Click(object? sender, EventArgs e) {
 			if (!Config.IsCustomNotificationPositionSet) {
 				Config.CustomNotificationPosition = notification.Location;
 			}
@@ -278,12 +278,12 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void comboBoxDisplay_SelectedValueChanged(object sender, EventArgs e) {
+		private void comboBoxDisplay_SelectedValueChanged(object? sender, EventArgs e) {
 			Config.NotificationDisplay = comboBoxDisplay.SelectedIndex;
 			notification.ShowExampleNotification(false);
 		}
 
-		private void trackBarEdgeDistance_ValueChanged(object sender, EventArgs e) {
+		private void trackBarEdgeDistance_ValueChanged(object? sender, EventArgs e) {
 			labelEdgeDistanceValue.Text = trackBarEdgeDistance.Value + " px";
 			Config.NotificationEdgeDistance = trackBarEdgeDistance.Value;
 			notification.ShowExampleNotification(false);
@@ -293,7 +293,7 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region Size
 
-		private void radioSize_CheckedChanged(object sender, EventArgs e) {
+		private void radioSize_CheckedChanged(object? sender, EventArgs e) {
 			if (radioSizeAuto.Checked) {
 				Config.NotificationSize = DesktopNotification.Size.Auto;
 			}
@@ -301,7 +301,7 @@ namespace TweetDuck.Dialogs.Settings {
 			notification.ShowExampleNotification(false);
 		}
 
-		private void radioSizeCustom_Click(object sender, EventArgs e) {
+		private void radioSizeCustom_Click(object? sender, EventArgs e) {
 			if (!Config.IsCustomNotificationSizeSet) {
 				Config.CustomNotificationSize = notification.BrowserSize;
 			}
@@ -310,7 +310,7 @@ namespace TweetDuck.Dialogs.Settings {
 			notification.ShowExampleNotification(false);
 		}
 
-		private void trackBarScrollSpeed_ValueChanged(object sender, EventArgs e) {
+		private void trackBarScrollSpeed_ValueChanged(object? sender, EventArgs e) {
 			if (trackBarScrollSpeed.AlignValueToTick()) {
 				labelScrollSpeedValue.Text = trackBarScrollSpeed.Value + "%";
 				Config.NotificationScrollSpeed = trackBarScrollSpeed.Value;

windows/TweetDuck/Dialogs/Settings/TabSettingsSounds.cs

@@ -51,11 +51,11 @@ namespace TweetDuck.Dialogs.Settings {
 			return canPlay;
 		}
 
-		private void tbCustomSound_TextChanged(object sender, EventArgs e) {
+		private void tbCustomSound_TextChanged(object? sender, EventArgs e) {
 			RefreshCanPlay();
 		}
 
-		private void btnPlaySound_Click(object sender, EventArgs e) {
+		private void btnPlaySound_Click(object? sender, EventArgs e) {
 			if (RefreshCanPlay()) {
 				Config.NotificationSoundPath = tbCustomSound.Text;
 				Config.NotificationSoundVolume = trackBarVolume.Value;
@@ -63,7 +63,7 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnBrowseSound_Click(object sender, EventArgs e) {
+		private void btnBrowseSound_Click(object? sender, EventArgs e) {
 			using OpenFileDialog dialog = new OpenFileDialog {
 				AutoUpgradeEnabled = true,
 				DereferenceLinks = true,
@@ -84,17 +84,17 @@ namespace TweetDuck.Dialogs.Settings {
 			}
 		}
 
-		private void btnResetSound_Click(object sender, EventArgs e) {
+		private void btnResetSound_Click(object? sender, EventArgs e) {
 			tbCustomSound.Text = string.Empty;
 		}
 
-		private void trackBarVolume_ValueChanged(object sender, EventArgs e) {
+		private void trackBarVolume_ValueChanged(object? sender, EventArgs e) {
 			volumeUpdateTimer.Stop();
 			volumeUpdateTimer.Start();
 			labelVolumeValue.Text = trackBarVolume.Value + "%";
 		}
 
-		private void volumeUpdateTimer_Tick(object sender, EventArgs e) {
+		private void volumeUpdateTimer_Tick(object? sender, EventArgs e) {
 			Config.NotificationSoundVolume = trackBarVolume.Value;
 			volumeUpdateTimer.Stop();
 		}

windows/TweetDuck/Dialogs/Settings/TabSettingsTray.cs

@@ -29,12 +29,12 @@ namespace TweetDuck.Dialogs.Settings {
 
 		#region System Tray
 
-		private void comboBoxTrayType_SelectedIndexChanged(object sender, EventArgs e) {
+		private void comboBoxTrayType_SelectedIndexChanged(object? sender, EventArgs e) {
 			Config.TrayBehavior = (TrayIcon.Behavior) comboBoxTrayType.SelectedIndex;
 			checkTrayHighlight.Enabled = Config.TrayBehavior.ShouldDisplayIcon();
 		}
 
-		private void checkTrayHighlight_CheckedChanged(object sender, EventArgs e) {
+		private void checkTrayHighlight_CheckedChanged(object? sender, EventArgs e) {
 			Config.EnableTrayHighlight = checkTrayHighlight.Checked;
 		}
 

windows/TweetDuck/Management/BrowserCache.cs

@@ -11,7 +11,7 @@ namespace TweetDuck.Management {
 		private static string CacheFolder => CefUtils.GetCacheFolder(App.StoragePath);
 
 		private static bool clearOnExit;
-		private static Timer autoClearTimer;
+		private static Timer? autoClearTimer;
 
 		private static long CalculateCacheSize() {
 			return new DirectoryInfo(CacheFolder).EnumerateFiles().Select(file => {

windows/TweetDuck/Management/FormManager.cs

@@ -28,12 +28,12 @@ namespace TweetDuck.Management {
 			}
 		}
 
-		public static T TryFind<T>() where T : Form {
+		public static T? TryFind<T>() where T : Form {
 			return OpenForms.OfType<T>().FirstOrDefault();
 		}
 
 		public static bool TryBringToFront<T>() where T : Form {
-			T form = TryFind<T>();
+			T? form = TryFind<T>();
 
 			if (form != null) {
 				form.BringToFront();

windows/TweetDuck/Management/ProfileManager.cs

@@ -61,7 +61,7 @@ namespace TweetDuck.Management {
 				}
 
 				if (items.HasFlag(Items.Session)) {
-					string authToken = ReadAuthCookie();
+					string? authToken = ReadAuthCookie();
 
 					if (authToken != null) {
 						stream.WriteString("cookie.auth", authToken);
@@ -84,9 +84,8 @@ namespace TweetDuck.Management {
 
 			try {
 				using CombinedFileStream stream = new CombinedFileStream(new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.None));
-				string key;
 
-				while ((key = stream.SkipFile()) != null) {
+				while (stream.SkipFile() is {} key) {
 					switch (key) {
 						case "config":
 							items |= Items.UserConfig;
@@ -121,9 +120,7 @@ namespace TweetDuck.Management {
 				bool oldCookies = false;
 
 				using (CombinedFileStream stream = new CombinedFileStream(new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.None))) {
-					CombinedFileStream.Entry entry;
+					while (stream.ReadFile() is {} entry) {
-
-					while ((entry = stream.ReadFile()) != null) {
 						switch (entry.KeyName) {
 							case "config":
 								if (items.HasFlag(Items.UserConfig)) {
@@ -223,11 +220,11 @@ namespace TweetDuck.Management {
 
 			public PathInfo(string fullPath, int rootLength) {
 				this.Full = fullPath;
-				this.Relative = fullPath.Substring(rootLength).TrimStart(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar); // strip leading separator character
+				this.Relative = fullPath[rootLength..].TrimStart(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar); // strip leading separator character
 			}
 		}
 
-		private static string ReadAuthCookie() {
+		private static string? ReadAuthCookie() {
 			using var cookieManager = Cef.GetGlobalCookieManager();
 
 			foreach (var cookie in cookieManager.VisitUrlCookiesAsync(AuthCookieUrl, true).Result) {

windows/TweetDuck/Management/VideoPlayer.cs

@@ -16,11 +16,11 @@ namespace TweetDuck.Management {
 
 		public bool Running => currentInstance is { Running: true };
 
-		public event EventHandler ProcessExited;
+		public event EventHandler? ProcessExited;
 
 		private readonly FormBrowser owner;
 
-		private Instance currentInstance;
+		private Instance? currentInstance;
 		private bool isClosing;
 
 		public VideoPlayer(FormBrowser owner) {
@@ -44,7 +44,7 @@ namespace TweetDuck.Management {
 					RedirectStandardOutput = true
 				};
 
-				Process process;
+				Process? process;
 				if ((process = Process.Start(startInfo)) != null) {
 					currentInstance = new Instance(process, pipe, videoUrl, tweetUrl, username);
 
@@ -69,7 +69,7 @@ namespace TweetDuck.Management {
 			currentInstance?.Pipe.Write("key", ((int) key).ToString());
 		}
 
-		private void pipe_DataIn(object sender, DuplexPipe.PipeReadEventArgs e) {
+		private void pipe_DataIn(object? sender, DuplexPipe.PipeReadEventArgs e) {
 			owner.InvokeSafe(() => {
 				switch (e.Key) {
 					case "vol":
@@ -128,19 +128,19 @@ namespace TweetDuck.Management {
 			}
 		}
 
-		private void owner_FormClosing(object sender, FormClosingEventArgs e) {
+		private void owner_FormClosing(object? sender, FormClosingEventArgs e) {
 			if (currentInstance != null) {
 				currentInstance.Process.Exited -= process_Exited;
 			}
 		}
 
-		private void process_OutputDataReceived(object sender, DataReceivedEventArgs e) {
+		private void process_OutputDataReceived(object? sender, DataReceivedEventArgs e) {
 			if (!string.IsNullOrEmpty(e.Data)) {
 				App.Logger.Debug("[VideoPlayer] " + e.Data);
 			}
 		}
 
-		private void process_Exited(object sender, EventArgs e) {
+		private void process_Exited(object? sender, EventArgs e) {
 			if (currentInstance == null) {
 				return;
 			}

windows/TweetDuck/Management/WindowsSessionManager.cs

@@ -5,18 +5,18 @@ using Win = System.Windows.Forms;
 namespace TweetDuck.Management {
 	static class WindowsSessionManager {
 		public static bool IsLocked { get; private set; } = false;
-		public static event EventHandler LockStateChanged;
+		public static event EventHandler? LockStateChanged;
 
 		public static void Register() {
 			Win.Application.ApplicationExit += OnApplicationExit;
 			SystemEvents.SessionSwitch += OnSessionSwitch;
 		}
 
-		private static void OnApplicationExit(object sender, EventArgs e) {
+		private static void OnApplicationExit(object? sender, EventArgs e) {
 			SystemEvents.SessionSwitch -= OnSessionSwitch;
 		}
 
-		private static void OnSessionSwitch(object sender, SessionSwitchEventArgs e) {
+		private static void OnSessionSwitch(object? sender, SessionSwitchEventArgs e) {
 			var reason = e.Reason;
 			if (reason == SessionSwitchReason.SessionLock) {
 				SetLocked(true);

windows/TweetDuck/Plugins/PluginControl.cs

@@ -16,9 +16,11 @@ namespace TweetDuck.Plugins {
 
 		private int nextHeight;
 
+		#pragma warning disable CS8618
 		private PluginControl() {
 			InitializeComponent();
 		}
+		#pragma warning restore CS8618
 
 		public PluginControl(PluginManager pluginManager, Plugin plugin) : this() {
 			this.pluginManager = pluginManager;
@@ -49,13 +51,13 @@ namespace TweetDuck.Plugins {
 			panelDescription_Resize(panelDescription, EventArgs.Empty);
 		}
 
-		private void timerLayout_Tick(object sender, EventArgs e) {
+		private void timerLayout_Tick(object? sender, EventArgs e) {
 			timerLayout.Stop();
 			Height = nextHeight;
 			ResumeLayout();
 		}
 
-		private void panelDescription_Resize(object sender, EventArgs e) {
+		private void panelDescription_Resize(object? sender, EventArgs e) {
 			SuspendLayout();
 
 			int maxWidth = panelDescription.Width - (panelDescription.VerticalScroll.Visible ? SystemInformation.VerticalScrollBarWidth : 0);
@@ -80,18 +82,18 @@ namespace TweetDuck.Plugins {
 			}
 		}
 
-		private void labelWebsite_Click(object sender, EventArgs e) {
+		private void labelWebsite_Click(object? sender, EventArgs e) {
 			if (labelWebsite.Text.Length > 0) {
 				App.SystemHandler.OpenBrowser(labelWebsite.Text);
 			}
 		}
 
-		private void btnConfigure_Click(object sender, EventArgs e) {
+		private void btnConfigure_Click(object? sender, EventArgs e) {
 			pluginManager.ConfigurePlugin(plugin);
 			ParentForm?.Close();
 		}
 
-		private void btnToggleState_Click(object sender, EventArgs e) {
+		private void btnToggleState_Click(object? sender, EventArgs e) {
 			pluginManager.Config.SetEnabled(plugin, !pluginManager.Config.IsEnabled(plugin));
 			pluginManager.Config.Save();
 			UpdatePluginState();

windows/TweetDuck/Program.cs

@@ -36,11 +36,11 @@ namespace TweetDuck {
 
 		public static string ExecutablePath => Win.Application.ExecutablePath;
 
-		private static Reporter errorReporter;
+		private static Reporter? errorReporter;
-		private static LockManager lockManager;
+		private static LockManager lockManager = null!;
 		private static bool hasCleanedUp;
 
-		public static ConfigObjects<UserConfig, SystemConfig> Config { get; private set; }
+		public static ConfigObjects<UserConfig, SystemConfig> Config { get; private set; } = null!;
 
 		internal static void SetupWinForms() {
 			Win.Application.EnableVisualStyles();
@@ -85,8 +85,8 @@ namespace TweetDuck {
 		private sealed class Setup : IAppSetup {
 			public bool IsPortable => File.Exists(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "makeportable"));
 			public bool IsDebugLogging => Arguments.HasFlag(Arguments.ArgLogging);
-			public string CustomDataFolder => Arguments.GetValue(Arguments.ArgDataFolder);
+			public string? CustomDataFolder => Arguments.GetValue(Arguments.ArgDataFolder);
-			public string ResourceRewriteRules => Arguments.GetValue(Arguments.ArgFreeze);
+			public string? ResourceRewriteRules => Arguments.GetValue(Arguments.ArgFreeze);
 
 			public ConfigManager CreateConfigManager(string storagePath) {
 				return new ConfigManager<UserConfig, SystemConfig>(storagePath, Config);
@@ -153,7 +153,7 @@ namespace TweetDuck {
 			}
 		}
 
-		private static void OnUnhandledException(object sender, UnhandledExceptionEventArgs e) {
+		private static void OnUnhandledException(object? sender, UnhandledExceptionEventArgs e) {
 			if (e.ExceptionObject is Exception ex) {
 				const string title = "TweetDuck Has Failed :(";
 				string message = "An unhandled exception has occurred: " + ex.Message;
@@ -173,7 +173,7 @@ namespace TweetDuck {
 		}
 
 		public static void RestartWithArgs(CommandLineArgs args) {
-			FormBrowser browserForm = FormManager.TryFind<FormBrowser>();
+			FormBrowser? browserForm = FormManager.TryFind<FormBrowser>();
 
 			if (browserForm != null) {
 				browserForm.ForceClose();

windows/TweetDuck/Reporter.cs

@@ -9,7 +9,7 @@ using TweetLib.Core.Application;
 
 namespace TweetDuck {
 	sealed class Reporter : IAppErrorHandler {
-		private static void Exit(string message, Exception ex = null) {
+		private static void Exit(string message, Exception? ex = null) {
 			try {
 				Process.GetCurrentProcess().Kill();
 			} catch {

windows/TweetDuck/Updates/FormUpdateDownload.cs

@@ -16,11 +16,11 @@ namespace TweetDuck.Updates {
 			timerDownloadCheck.Start();
 		}
 
-		private void btnCancel_Click(object sender, EventArgs e) {
+		private void btnCancel_Click(object? sender, EventArgs e) {
 			Close();
 		}
 
-		private void timerDownloadCheck_Tick(object sender, EventArgs e) {
+		private void timerDownloadCheck_Tick(object? sender, EventArgs e) {
 			if (updateInfo.DownloadStatus.IsFinished(false)) {
 				timerDownloadCheck.Stop();
 				DialogResult = DialogResult.OK;

windows/TweetDuck/Updates/UpdateCheckClient.cs

@@ -33,7 +33,7 @@ namespace TweetDuck.Updates {
 					result.SetCanceled();
 				}
 				else if (task.IsFaulted) {
-					result.SetException(ExpandWebException(task.Exception.InnerException));
+					result.SetException(ExpandWebException(task.Exception!.InnerException));
 				}
 				else {
 					try {
@@ -65,7 +65,7 @@ namespace TweetDuck.Updates {
 			return new UpdateInfo(versionTag, releaseNotes, downloadUrl, installerFolder);
 		}
 
-		private static Exception ExpandWebException(Exception e) {
+		private static Exception ExpandWebException(Exception? e) {
 			if (e is WebException { Response: HttpWebResponse response } ) {
 				try {
 					using var stream = response.GetResponseStream();
@@ -76,7 +76,7 @@ namespace TweetDuck.Updates {
 				}
 			}
 
-			return e;
+			return e!;
 		}
 	}
 }

windows/TweetDuck/Utils/BrowserUtils.cs

@@ -38,7 +38,7 @@ namespace TweetDuck.Utils {
 			args["disable-plugins-discovery"] = "1";
 			args["enable-system-flash"] = "0";
 
-			if (args.TryGetValue("js-flags", out string jsFlags)) {
+			if (args.TryGetValue("js-flags", out var jsFlags)) {
 				args["js-flags"] = "--expose-gc " + jsFlags;
 			}
 			else {
@@ -63,7 +63,7 @@ namespace TweetDuck.Utils {
 				host.SetZoomLevel(Math.Log(percentage / 100.0, 1.2));
 			}
 
-			void UpdateZoomLevel(object sender, EventArgs args) {
+			void UpdateZoomLevel(object? sender, EventArgs args) {
 				SetZoomLevel(browser.GetBrowserHost(), Config.ZoomLevel);
 			}
 

windows/TweetDuck/Utils/NativeMethods.cs

@@ -62,7 +62,7 @@ namespace TweetDuck.Utils {
 		[DllImport("user32.dll")]
 		private static extern bool PostMessage(IntPtr hWnd, uint msg, UIntPtr wParam, IntPtr lParam);
 
-		[DllImport("user32.dll")]
+		[DllImport("user32.dll", CharSet = CharSet.Unicode)]
 		public static extern uint RegisterWindowMessage(string messageName);
 
 		[DllImport("user32.dll")]

windows/TweetDuck/Utils/WindowsUtils.cs

@@ -43,28 +43,28 @@ namespace TweetDuck.Utils {
 		public static IEnumerable<Browser> FindInstalledBrowsers() {
 			static IEnumerable<Browser> ReadBrowsersFromKey(RegistryHive hive) {
 				using RegistryKey root = RegistryKey.OpenBaseKey(hive, RegistryView.Default);
-				using RegistryKey browserList = root.OpenSubKey(@"SOFTWARE\Clients\StartMenuInternet", false);
+				using RegistryKey? browserList = root.OpenSubKey(@"SOFTWARE\Clients\StartMenuInternet", false);
 
 				if (browserList == null) {
 					yield break;
 				}
 
 				foreach (string sub in browserList.GetSubKeyNames()) {
-					using RegistryKey browserKey = browserList.OpenSubKey(sub, false);
+					using RegistryKey? browserKey = browserList.OpenSubKey(sub, false);
-					using RegistryKey shellKey = browserKey?.OpenSubKey(@"shell\open\command");
+					using RegistryKey? shellKey = browserKey?.OpenSubKey(@"shell\open\command");
 
-					if (shellKey == null) {
+					if (browserKey == null || shellKey == null) {
 						continue;
 					}
 
-					string browserName = browserKey.GetValue(null) as string;
+					string? browserName = browserKey.GetValue(null) as string;
-					string browserPath = shellKey.GetValue(null) as string;
+					string? browserPath = shellKey.GetValue(null) as string;
 
 					if (string.IsNullOrEmpty(browserName) || string.IsNullOrEmpty(browserPath)) {
 						continue;
 					}
 
-					if (browserPath[0] == '"' && browserPath[browserPath.Length - 1] == '"') {
+					if (browserPath[0] == '"' && browserPath[^1] == '"') {
 						browserPath = browserPath.Substring(1, browserPath.Length - 2);
 					}
 
@@ -94,7 +94,7 @@ namespace TweetDuck.Utils {
 			}
 
 			public override int GetHashCode() => Name.GetHashCode();
-			public override bool Equals(object obj) => obj is Browser other && Name == other.Name;
+			public override bool Equals(object? obj) => obj is Browser other && Name == other.Name;
 			public override string ToString() => Name;
 		}
 	}

windows/TweetImpl.CefSharp/Adapters/CefErrorCodeAdapter.cs

@@ -12,7 +12,7 @@ namespace TweetImpl.CefSharp.Adapters {
 			return errorCode == CefErrorCode.Aborted;
 		}
 
-		public string GetName(CefErrorCode errorCode) {
+		public string? GetName(CefErrorCode errorCode) {
 			return Enum.GetName(typeof(CefErrorCode), errorCode);
 		}
 	}

windows/TweetImpl.CefSharp/Adapters/CefJsDialogCallbackAdapter.cs

@@ -7,7 +7,7 @@ namespace TweetImpl.CefSharp.Adapters {
 
 		private CefJsDialogCallbackAdapter() {}
 
-		public void Continue(IJsDialogCallback callback, bool success, string userInput = null) {
+		public void Continue(IJsDialogCallback callback, bool success, string? userInput = null) {
 			if (userInput == null) {
 				callback.Continue(success);
 			}

windows/TweetImpl.CefSharp/Adapters/CefResponseAdapter.cs

@@ -24,7 +24,7 @@ namespace TweetImpl.CefSharp.Adapters {
 			response.SetHeaderByName(header, value, overwrite: true);
 		}
 
-		public string GetHeader(IResponse response, string header) {
+		public string? GetHeader(IResponse response, string header) {
 			return response.Headers[header];
 		}
 	}

windows/TweetImpl.CefSharp/Component/BrowserComponentBase.cs

@@ -10,7 +10,7 @@ using IContextMenuHandler = TweetLib.Browser.Interfaces.IContextMenuHandler;
 
 namespace TweetImpl.CefSharp.Component {
 	public abstract class BrowserComponentBase : BrowserComponent<IFrame, IRequest> {
-		public delegate CefContextMenuHandler CreateContextMenu(IContextMenuHandler handler);
+		public delegate CefContextMenuHandler CreateContextMenu(IContextMenuHandler? handler);
 
 		public ResourceHandlerRegistry<IResourceHandler> ResourceHandlerRegistry { get; } = new ResourceHandlerRegistry<IResourceHandler>(CefResourceHandlerFactory.Instance);
 
@@ -50,19 +50,19 @@ namespace TweetImpl.CefSharp.Component {
 			browser.JavascriptObjectRepository.Register(name, bridge);
 		}
 
-		private void OnLoadingStateChanged(object sender, LoadingStateChangedEventArgs e) {
+		private void OnLoadingStateChanged(object? sender, LoadingStateChangedEventArgs e) {
 			base.OnLoadingStateChanged(e.IsLoading);
 		}
 
-		private void OnLoadError(object sender, LoadErrorEventArgs e) {
+		private void OnLoadError(object? sender, LoadErrorEventArgs e) {
 			base.OnLoadError(e.FailedUrl, e.ErrorCode, CefErrorCodeAdapter.Instance);
 		}
 
-		private void OnFrameLoadStart(object sender, FrameLoadStartEventArgs e) {
+		private void OnFrameLoadStart(object? sender, FrameLoadStartEventArgs e) {
 			base.OnFrameLoadStart(e.Url, e.Frame);
 		}
 
-		private void OnFrameLoadEnd(object sender, FrameLoadEndEventArgs e) {
+		private void OnFrameLoadEnd(object? sender, FrameLoadEndEventArgs e) {
 			base.OnFrameLoadEnd(e.Url, e.Frame);
 		}
 	}

windows/TweetImpl.CefSharp/Handlers/CefByteArrayResourceHandler.cs

@@ -12,25 +12,27 @@ namespace TweetImpl.CefSharp.Handlers {
 			dataOut.Write(dataIn, position, length);
 		};
 
-		private ByteArrayResourceHandlerLogic<IResponse> logic;
+		private static ByteArrayResourceHandlerLogic<IResponse> CreateLogic(ByteArrayResource resource) {
-
+			return new ByteArrayResourceHandlerLogic<IResponse>(resource, CefResponseAdapter.Instance);
-		public CefByteArrayResourceHandler() {
-			SetResource(new ByteArrayResource(Array.Empty<byte>()));
 		}
 
+		private ByteArrayResourceHandlerLogic<IResponse> logic;
+
+		public CefByteArrayResourceHandler() : this(new ByteArrayResource(Array.Empty<byte>())) {}
+
 		internal CefByteArrayResourceHandler(ByteArrayResource resource) {
-			SetResource(resource);
+			this.logic = CreateLogic(resource);
 		}
 
 		public void SetResource(ByteArrayResource resource) {
-			this.logic = new ByteArrayResourceHandlerLogic<IResponse>(resource, CefResponseAdapter.Instance);
+			this.logic = CreateLogic(resource);
 		}
 
 		bool IResourceHandler.Open(IRequest request, out bool handleRequest, ICallback callback) {
 			return logic.Open(out handleRequest);
 		}
 
-		void IResourceHandler.GetResponseHeaders(IResponse response, out long responseLength, out string redirectUrl) {
+		void IResourceHandler.GetResponseHeaders(IResponse response, out long responseLength, out string? redirectUrl) {
 			logic.GetResponseHeaders(response, out responseLength, out redirectUrl);
 		}
 

windows/TweetImpl.CefSharp/Handlers/CefContextMenuHandler.cs

@@ -7,7 +7,7 @@ namespace TweetImpl.CefSharp.Handlers {
 	public abstract class CefContextMenuHandler : IContextMenuHandler {
 		private readonly ContextMenuLogic<IMenuModel> logic;
 
-		protected CefContextMenuHandler(TweetLib.Browser.Interfaces.IContextMenuHandler handler) {
+		protected CefContextMenuHandler(TweetLib.Browser.Interfaces.IContextMenuHandler? handler) {
 			this.logic = new ContextMenuLogic<IMenuModel>(handler, CefMenuModelAdapter.Instance);
 		}
 

windows/TweetImpl.CefSharp/Handlers/CefLifeSpanHandler.cs

@@ -12,7 +12,7 @@ namespace TweetImpl.CefSharp.Handlers {
 			this.Logic = new LifeSpanHandlerLogic(popupHandler);
 		}
 
-		protected override bool OnBeforePopup(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, string targetUrl, string targetFrameName, WindowOpenDisposition targetDisposition, bool userGesture, IPopupFeatures popupFeatures, IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser newBrowser) {
+		protected override bool OnBeforePopup(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, string targetUrl, string targetFrameName, WindowOpenDisposition targetDisposition, bool userGesture, IPopupFeatures popupFeatures, IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser? newBrowser) {
 			newBrowser = null;
 			return Logic.OnBeforePopup(targetUrl, ConvertTargetDisposition(targetDisposition));
 		}

windows/TweetImpl.CefSharp/Handlers/CefResourceRequestHandler.cs

@@ -9,7 +9,7 @@ namespace TweetImpl.CefSharp.Handlers {
 	sealed class CefResourceRequestHandler : ResourceRequestHandler {
 		private readonly ResourceRequestHandlerLogic<IRequest, IResponse, IResourceHandler> logic;
 
-		public CefResourceRequestHandler(ResourceHandlerRegistry<IResourceHandler> resourceHandlerRegistry, IResourceRequestHandler resourceRequestHandler) {
+		public CefResourceRequestHandler(ResourceHandlerRegistry<IResourceHandler> resourceHandlerRegistry, IResourceRequestHandler? resourceRequestHandler) {
 			this.logic = new ResourceRequestHandlerLogic<IRequest, IResponse, IResourceHandler>(CefRequestAdapter.Instance, CefResponseAdapter.Instance, resourceHandlerRegistry, resourceRequestHandler);
 		}
 
@@ -17,11 +17,11 @@ namespace TweetImpl.CefSharp.Handlers {
 			return logic.OnBeforeResourceLoad(request, callback) ? CefReturnValue.Continue : CefReturnValue.Cancel;
 		}
 
-		protected override IResourceHandler GetResourceHandler(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request) {
+		protected override IResourceHandler? GetResourceHandler(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request) {
 			return logic.GetResourceHandler(request);
 		}
 
-		protected override IResponseFilter GetResourceResponseFilter(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response) {
+		protected override IResponseFilter? GetResourceResponseFilter(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response) {
 			return CefResponseFilter.Create(logic.GetResourceResponseFilter(request, response));
 		}
 

windows/TweetImpl.CefSharp/Handlers/CefResourceRequestHandlerFactory.cs

@@ -11,7 +11,7 @@ namespace TweetImpl.CefSharp.Handlers {
 
 		private readonly ResourceRequestHandlerFactoryLogic<CefResourceRequestHandler, IResourceHandler, IRequest> logic;
 
-		public CefResourceRequestHandlerFactory(IResourceRequestHandler resourceRequestHandler, ResourceHandlerRegistry<IResourceHandler> registry) {
+		public CefResourceRequestHandlerFactory(IResourceRequestHandler? resourceRequestHandler, ResourceHandlerRegistry<IResourceHandler> registry) {
 			this.logic = new ResourceRequestHandlerFactoryLogic<CefResourceRequestHandler, IResourceHandler, IRequest>(CefRequestAdapter.Instance, new CefResourceRequestHandler(registry, resourceRequestHandler), registry);
 		}