Refactor web form validation and yielding after submitting

Server/Phantom.Server.Web.Components/Forms/Form.razor

@@ -22,7 +22,9 @@
   
   private async Task Submit(EditContext obj) {
     BeforeSubmit?.Invoke(this, EventArgs.Empty);
-    await OnSubmit.InvokeAsync(obj);
+    if (obj.Validate()) {
+      await OnSubmit.InvokeAsync(obj);
+    }
   }
 
   public void Dispose() {

Server/Phantom.Server.Web.Components/Forms/FormButtonSubmit.cs

@@ -44,9 +44,10 @@ public sealed class FormButtonSubmit : ComponentBase {
 		public bool IsSubmitting { get; private set; }
 		public string? SubmitError { get; private set; }
 
-		public void StartSubmitting() {
+		public async Task StartSubmitting() {
 			IsSubmitting = true;
 			SubmitError = null;
+			await Task.Yield();
 		}
 		
 		public void StopSubmitting(string? error = null) {

Server/Phantom.Server.Web/Pages/InstanceCreate.razor

@@ -279,17 +279,12 @@
   }
 
   private async Task Submit(EditContext context) {
-    if (!context.Validate()) {
-      return;
-    }
-
     var selectedAgent = form.SelectedAgent;
     if (selectedAgent == null) {
       return;
     }
 
-    form.SubmitModel.StartSubmitting();
-    await Task.Yield();
+    await form.SubmitModel.StartSubmitting();
 
     var serverPort = (ushort) form.ServerPort;
     var rconPort = (ushort) form.RconPort;

Server/Phantom.Server.Web/Pages/Login.razor

@@ -47,11 +47,7 @@
   }
 
   private async Task DoLogin(EditContext context) {
-    if (!context.Validate()) {
-      return;
-    }
-    
-    form.SubmitModel.StartSubmitting();
+    await form.SubmitModel.StartSubmitting();
     
     string? returnUrl = Navigation.GetQueryParameter("return", out var url) ? url : null;
     var result = await LoginManager.SignIn(form.Username, form.Password, returnUrl);

Server/Phantom.Server.Web/Pages/Setup.razor

@@ -56,11 +56,7 @@
   }
 
   private async Task DoLogin(EditContext context) {
-    if (!context.Validate()) {
-      return;
-    }
-
-    form.SubmitModel.StartSubmitting();
+    await form.SubmitModel.StartSubmitting();
 
     if (!IsAdministratorTokenValid()) {
       form.SubmitModel.StopSubmitting("Invalid administrator token.");

Server/Phantom.Server.Web/Shared/InstanceStopForm.razor

@@ -55,13 +55,8 @@
   }
 
   private async Task StopInstance(EditContext context) {
-    if (!context.Validate()) {
-      return;
-    }
-    
-    form.SubmitModel.StartSubmitting();
-    await Task.Yield();
-    
+    await form.SubmitModel.StartSubmitting();
+
     var result = await InstanceManager.StopInstance(InstanceGuid, new MinecraftStopStrategy(form.StopInSeconds));
     if (result == StopInstanceResult.StopInitiated) {
       await AuditLog.AddInstanceStoppedEvent(InstanceGuid, form.StopInSeconds);
@@ -72,4 +67,5 @@
       form.SubmitModel.StopSubmitting(result.ToSentence());
     }
   }
+
 }

Server/Phantom.Server.Web/Shared/UserAddDialog.razor

@@ -49,11 +49,7 @@
   }
 
   private async Task AddUser(EditContext context) {
-    if (!context.Validate()) {
-      return;
-    }
-
-    form.SubmitModel.StartSubmitting();
+    await form.SubmitModel.StartSubmitting();
 
     var user = new IdentityUser(form.Username);
     var result = await UserManager.CreateAsync(user, form.Password);

Server/Phantom.Server.Web/Shared/UserDeleteDialog.razor

@@ -36,7 +36,7 @@
   }
 
   private async Task DeleteUser() {
-    submitModel.StartSubmitting();
+    await submitModel.StartSubmitting();
 
     if (userToDelete == null) {
       submitModel.StopSubmitting("Invalid user.");