Add a locking mechanism to avoid multiple simultaneous processes

Configuration/LockManager.cs

@@ -0,0 +1,108 @@
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Threading;
+
+namespace TweetDick.Configuration{
+    class LockManager{
+        private readonly string file;
+        private FileStream lockStream;
+        private Process lockingProcess;
+
+        public LockManager(string file){
+            this.file = file;
+        }
+
+        private bool CreateLockFile(){
+            if (lockStream != null){
+                throw new InvalidOperationException("Lock file already exists.");
+            }
+
+            try{
+                lockStream = new FileStream(file,FileMode.Create,FileAccess.Write,FileShare.Read);
+
+                byte[] id = BitConverter.GetBytes(Process.GetCurrentProcess().Id);
+                lockStream.Write(id,0,id.Length);
+                lockStream.Flush();
+
+                if (lockingProcess != null){
+                    lockingProcess.Close();
+                    lockingProcess = null;
+                }
+
+                return true;
+            }catch(Exception){
+                if (lockStream != null){
+                    lockStream.Close();
+                    lockStream.Dispose();
+                }
+
+                return false;
+            }
+        }
+
+        public bool Lock(){
+            if (lockStream != null)return true;
+
+            try{
+                byte[] bytes = new byte[4];
+
+                using(FileStream fileStream = new FileStream(file,FileMode.Open,FileAccess.Read,FileShare.ReadWrite)){
+                    fileStream.Read(bytes,0,4);
+                }
+
+                int pid = BitConverter.ToInt32(bytes,0);
+
+                try{
+                    lockingProcess = Process.GetProcessById(pid);
+                }catch(ArgumentException){}
+
+                return lockingProcess == null && CreateLockFile();
+            }catch(DirectoryNotFoundException){
+                string dir = Path.GetDirectoryName(file);
+
+                if (dir != null){
+                    Directory.CreateDirectory(dir);
+                    return CreateLockFile();
+                }
+            }catch(FileNotFoundException){
+                return CreateLockFile();
+            }catch(Exception e){
+                return false;
+            }
+
+            return false;
+        }
+
+        public void Unlock(){
+            if (lockStream != null){
+                lockStream.Close();
+                lockStream.Dispose();
+                File.Delete(file);
+
+                lockStream = null;
+            }
+        }
+
+        public bool CloseLockingProcess(int timeout){
+            if (lockingProcess != null){
+                lockingProcess.CloseMainWindow();
+
+                for(int waited = 0; waited < timeout && !lockingProcess.HasExited;){
+                    lockingProcess.Refresh();
+
+                    Thread.Sleep(100);
+                    waited += 100;
+                }
+
+                if (lockingProcess.HasExited){
+                    lockingProcess.Close();
+                    lockingProcess = null;
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    }
+}

Program.cs

@@ -19,7 +19,9 @@ static class Program{
         #endif
 
         public static readonly string StoragePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),BrandName);
-        public static readonly UserConfig UserConfig;
+        private static readonly LockManager LockManager;
+        
+        public static UserConfig UserConfig { get; private set; }
 
         private static string HeaderAcceptLanguage{
             get{
@@ -35,7 +37,7 @@ private static string HeaderAcceptLanguage{
         }
 
         static Program(){
-            UserConfig = UserConfig.Load(Path.Combine(StoragePath,"TD_UserConfig.cfg"));
+            LockManager = new LockManager(Path.Combine(StoragePath,".lock"));
         }
 
         [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
@@ -48,6 +50,18 @@ static Program(){
         private static void Main(){
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
+            
+            if (!LockManager.Lock()){
+                if (MessageBox.Show("Another instance of "+BrandName+" is already running.\r\nDo you want to close it?",BrandName+" is Already Running",MessageBoxButtons.YesNo,MessageBoxIcon.Error,MessageBoxDefaultButton.Button2) == DialogResult.Yes){
+                    if (!LockManager.CloseLockingProcess(10000)){
+                        MessageBox.Show("Could not close the other process.",BrandName+" Has Failed :(",MessageBoxButtons.OK,MessageBoxIcon.Error);
+                        return;
+                    }
+                }
+                else return;
+            }
+
+            UserConfig = UserConfig.Load(Path.Combine(StoragePath,"TD_UserConfig.cfg"));
 
             MigrationManager.Run();
 
@@ -70,6 +84,7 @@ private static void Main(){
 
             Application.ApplicationExit += (sender, args) => {
                 UserConfig.Save();
+                LockManager.Unlock();
                 Cef.Shutdown();
             };
 

TweetDick.csproj

@@ -75,6 +75,7 @@
     <Reference Include="System.Windows.Forms" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Configuration\LockManager.cs" />
     <Compile Include="Configuration\UserConfig.cs" />
     <Compile Include="Core\Controls\FlatProgressBar.cs">
       <SubType>Component</SubType>