Improved cross threaded invocation.

LibationWinForms/AsyncNotifyPropertyChanged.cs

@@ -4,15 +4,13 @@ using System.Threading;
 
 namespace LibationWinForms
 {
-	public abstract class AsyncNotifyPropertyChanged : INotifyPropertyChanged
+	public abstract class AsyncNotifyPropertyChanged : SynchronizeInvoker, INotifyPropertyChanged
 	{
 		public event PropertyChangedEventHandler PropertyChanged;
-		private CrossThreadSync<PropertyChangedEventArgs> ThreadSync { get; } = new CrossThreadSync<PropertyChangedEventArgs>();
 
-		public AsyncNotifyPropertyChanged()
-			=>ThreadSync.ObjectReceived += (_, args) => PropertyChanged?.Invoke(this, args);		
+		public AsyncNotifyPropertyChanged() { }
 
 		protected void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
-			=> ThreadSync.Post(new PropertyChangedEventArgs(propertyName));
+			=>BeginInvoke(PropertyChanged, new object[] { this, new PropertyChangedEventArgs(propertyName) });
 	}
 }

LibationWinForms/BookLiberation/BaseForms/LiberationBaseForm.cs

@@ -11,15 +11,14 @@ namespace LibationWinForms.BookLiberation.BaseForms
 	{
 		protected IStreamable Streamable { get; private set; }
 		protected LogMe LogMe { get; private set; }
-		private CrossThreadSync<Action> FormSync { get; } = new CrossThreadSync<Action>();
+		private SynchronizeInvoker Invoker { get; init; } 
 
 		public LiberationBaseForm()
 		{
 			//SynchronizationContext.Current will be null until the process contains a Form.
 			//If this is the first form created, it will not exist until after execution
 			//reaches inside the constructor. So need to reset the context here.
-			FormSync.ResetContext();
-			FormSync.ObjectReceived += (_, action) => action();
+			Invoker = new SynchronizeInvoker();
 		}
 
 		public void RegisterFileLiberator(IStreamable streamable, LogMe logMe = null)
@@ -134,7 +133,7 @@ namespace LibationWinForms.BookLiberation.BaseForms
 		/// could cause it to freeze. Form.BeginInvoke won't work until the form is created 
 		/// (ie. shown) because Control doesn't get a window handle until it is Shown.
 		/// </summary>
-		private void OnStreamingBeginShow(object sender, string beginString) => FormSync.Send(Show);
+		private void OnStreamingBeginShow(object sender, string beginString) => Invoker.Invoke(Show);
 		
 		#endregion
 

LibationWinForms/CrossThreadSync[T].cs

@@ -1,45 +0,0 @@
-using System;
-using System.ComponentModel;
-using System.Threading;
-
-namespace LibationWinForms
-{
-	internal class CrossThreadSync<T>
-	{
-		public event EventHandler<T> ObjectReceived;
-		private int InstanceThreadId { get; set; } = Thread.CurrentThread.ManagedThreadId;
-		private SynchronizationContext SyncContext { get; set; } = SynchronizationContext.Current;
-		private bool InvokeRequired => Thread.CurrentThread.ManagedThreadId != InstanceThreadId;
-
-		public void ResetContext()
-		{
-			SyncContext = SynchronizationContext.Current;
-			InstanceThreadId = Thread.CurrentThread.ManagedThreadId;
-		}
-
-		public void Send(T obj)
-		{
-			if (InvokeRequired)
-				SyncContext.Send(SendOrPostCallback, new AsyncCompletedEventArgs(null, false, obj));
-			else
-				ObjectReceived?.Invoke(this, obj);
-		}
-
-		public void Post(T obj)
-		{
-			if (InvokeRequired)
-				SyncContext.Post(SendOrPostCallback, new AsyncCompletedEventArgs(null, false, obj));
-			else
-				ObjectReceived?.Invoke(this, obj);
-		}
-
-		private void SendOrPostCallback(object asyncArgs)
-		{
-			var e = asyncArgs as AsyncCompletedEventArgs;
-
-			var userObject = (T)e.UserState;
-
-			ObjectReceived?.Invoke(this, userObject);
-		}
-	}
-}

LibationWinForms/GridEntry.cs

@@ -96,7 +96,6 @@ namespace LibationWinForms
 		public string Description { get; }
 		public string DisplayTags => string.Join("\r\n", Book.UserDefinedItem.TagsEnumerated);
 		public (LiberatedState, PdfState) Liberate => (LibraryCommands.Liberated_Status(Book), LibraryCommands.Pdf_Status(Book));
-
 		#endregion
 
 		#region Data Sorting

LibationWinForms/SynchronizeInvoker.cs

@@ -0,0 +1,143 @@
+using System;
+using System.ComponentModel;
+using System.Threading;
+
+namespace LibationWinForms
+{
+	public class SynchronizeInvoker : ISynchronizeInvoke
+	{
+		public bool InvokeRequired => Thread.CurrentThread.ManagedThreadId != InstanceThreadId;
+		private int InstanceThreadId { get; set; } = Thread.CurrentThread.ManagedThreadId;
+		private SynchronizationContext SyncContext { get; init; } = SynchronizationContext.Current;
+
+		public SynchronizeInvoker()
+		{
+			SyncContext = SynchronizationContext.Current;
+			if (SyncContext is null)
+				throw new NullReferenceException($"Could not capture a current {nameof(SynchronizationContext)}");
+		}
+
+		public IAsyncResult BeginInvoke(Action action) => BeginInvoke(action, null);
+		public IAsyncResult BeginInvoke(Delegate method) => BeginInvoke(method, null);
+		public IAsyncResult BeginInvoke(Delegate method, object[] args)
+		{
+			var tme = new ThreadMethodEntry(method, args);
+
+			if (InvokeRequired)
+			{
+				SyncContext.Post(ThreadMethodEntry.OnSendOrPostCallback, tme);
+			}
+			else
+			{
+				tme.Complete();
+				tme.CompletedSynchronously = true;
+			}
+			return tme;
+		}
+
+		public object EndInvoke(IAsyncResult result)
+		{
+			if (result is not ThreadMethodEntry crossThread)
+				throw new ArgumentException($"{nameof(result)} was not returned by {nameof(BeginInvoke)}");
+
+			if (!crossThread.IsCompleted) 
+				crossThread.AsyncWaitHandle.WaitOne();
+
+			return crossThread.ReturnValue;
+		}
+
+		public object Invoke(Action action) => Invoke(action, null);
+		public object Invoke(Delegate method) => Invoke(method, null);
+		public object Invoke(Delegate method, object[] args)
+		{
+			var tme = new ThreadMethodEntry(method, args);
+
+			if (InvokeRequired)
+			{
+				SyncContext.Send(ThreadMethodEntry.OnSendOrPostCallback, tme);
+			}
+			else
+			{
+				tme.Complete();
+				tme.CompletedSynchronously = true;
+			}
+
+			return tme.ReturnValue;
+		}
+
+		private class ThreadMethodEntry : IAsyncResult
+		{
+			public object AsyncState => null;
+			public bool CompletedSynchronously { get; internal set; }
+			public bool IsCompleted { get; private set; }
+			public object ReturnValue { get; private set; }
+			public WaitHandle AsyncWaitHandle
+			{
+				get
+				{
+					if (resetEvent == null)
+					{
+						lock (invokeSyncObject)
+						{
+							if (resetEvent == null)
+							{
+								resetEvent = new ManualResetEvent(initialState: false);
+							}
+						}
+					}
+					return resetEvent;
+				}
+			}
+
+			private object invokeSyncObject = new object();
+			private Delegate method;
+			private object[] args;
+			private ManualResetEvent resetEvent;
+
+			public ThreadMethodEntry(Delegate method, object[] args)
+			{
+				this.method = method;
+				this.args = args;
+				resetEvent = new ManualResetEvent(initialState: false);				
+			}
+			/// <summary>
+			/// This callback executes on the SynchronizationContext thread.
+			/// </summary>
+			public static void OnSendOrPostCallback(object asyncArgs)
+			{
+				var e = asyncArgs as ThreadMethodEntry;
+
+				e.Complete();
+			}
+
+			public void Complete()
+			{
+				try
+				{
+					switch (method)
+					{
+						case Action actiton:
+							actiton();
+							break;
+						default:
+							ReturnValue = method.DynamicInvoke(args);
+							break;
+					}
+				}
+				finally
+				{
+					IsCompleted = true;
+					resetEvent.Set();
+				}
+			}
+
+			~ThreadMethodEntry()
+			{
+				if (resetEvent != null)
+				{
+					resetEvent.Close();
+				}
+			}
+		}
+	}
+}