Merge pull request #618 from lukasf/dev

Fix DispatcherHelper open issues

Author: deltakosh

Microsoft.Toolkit.Uwp/Helpers/DispatcherHelper.cs

@@ -42,7 +42,7 @@ public static Task<T> ExecuteOnUIThreadAsync<T>(Func<Task<T>> function, CoreDisp
         /// <param name="function">Asynchronous function to be executed asynchronously on UI thread</param>
         /// <param name="priority">Dispatcher execution priority, default is normal</param>
         /// <returns>Awaitable Task with type <typeparamref name="T"/></returns>
-        public static Task<T> ExecuteOnUIThreadAsync<T>(CoreApplicationView viewToExecuteOn, Func<Task<T>> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
+        public static Task<T> ExecuteOnUIThreadAsync<T>(this CoreApplicationView viewToExecuteOn, Func<Task<T>> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
             if (viewToExecuteOn == null)
             {
@@ -59,15 +59,14 @@ public static Task<T> ExecuteOnUIThreadAsync<T>(CoreApplicationView viewToExecut
         /// <param name="function">Asynchronous function to be executed asynchronously on UI thread</param>
         /// <param name="priority">Dispatcher execution priority, default is normal</param>
         /// <returns>Awaitable Task</returns>
-        public static Task ExecuteOnUIThreadAsync(CoreApplicationView viewToExecuteOn, Func<Task> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
+        public static Task ExecuteOnUIThreadAsync(this CoreApplicationView viewToExecuteOn, Func<Task> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
-            return ExecuteOnUIThreadAsync<object>(
-                viewToExecuteOn,
-                async () =>
-                {
-                    await function().ConfigureAwait(false);
-                    return null;
-                }, priority);
+            if (viewToExecuteOn == null)
+            {
+                throw new ArgumentNullException("viewToExecuteOn can't be null!");
+            }
+
+            return viewToExecuteOn.Dispatcher.AwaitableRunAsync(function, priority);
         }
 
         /// <summary>
@@ -78,12 +77,7 @@ public static Task ExecuteOnUIThreadAsync(CoreApplicationView viewToExecuteOn, F
         /// <returns>Awaitable Task</returns>
         public static Task ExecuteOnUIThreadAsync(Func<Task> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
-            return ExecuteOnUIThreadAsync<object>(
-                async () =>
-                {
-                    await function().ConfigureAwait(false);
-                    return null;
-                }, priority);
+            return ExecuteOnUIThreadAsync(CoreApplication.MainView, function, priority);
         }
 
         /// <summary>
@@ -93,7 +87,7 @@ public static Task ExecuteOnUIThreadAsync(Func<Task> function, CoreDispatcherPri
         /// <param name="function">Asynchronous function to be executed asynchronously on UI thread</param>
         /// <param name="priority">Dispatcher execution priority, default is normal</param>
         /// <returns>Awaitable Task/></returns>
-        public static Task ExecuteOnUIThreadAsync(CoreApplicationView viewToExecuteOn, Action function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
+        public static Task ExecuteOnUIThreadAsync(this CoreApplicationView viewToExecuteOn, Action function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
             if (viewToExecuteOn == null)
             {
@@ -122,7 +116,7 @@ public static Task ExecuteOnUIThreadAsync(Action function, CoreDispatcherPriorit
         /// <param name="function">Synchronous function with return type <typeparamref name="T"/> to be executed on UI thread</param>
         /// <param name="priority">Dispatcher execution priority, default is normal</param>
         /// <returns>Awaitable Task with type <typeparamref name="T"/></returns>
-        public static Task<T> ExecuteOnUIThreadAsync<T>(CoreApplicationView viewToExecuteOn, Func<T> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
+        public static Task<T> ExecuteOnUIThreadAsync<T>(this CoreApplicationView viewToExecuteOn, Func<T> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
             if (viewToExecuteOn == null)
             {
@@ -159,28 +153,28 @@ public static Task<T> AwaitableRunAsync<T>(this CoreDispatcher dispatcher, Func<
                 throw new ArgumentNullException("function can't be null!");
             }
 
-            TaskCompletionSource<T> taskCompletionSource = new TaskCompletionSource<T>();
+            var taskCompletionSource = new TaskCompletionSource<T>();
 
             var ignored = dispatcher.RunAsync(priority, async () =>
-             {
-                 try
-                 {
-                     var awaitableResult = function();
-                     if (awaitableResult != null)
-                     {
-                         var result = await awaitableResult.ConfigureAwait(false);
-                         taskCompletionSource.SetResult(result);
-                     }
-                     else
-                     {
-                         taskCompletionSource.SetResult(default(T));
-                     }
-                 }
-                 catch (Exception e)
-                 {
-                     taskCompletionSource.SetException(e);
-                 }
-             });
+            {
+                try
+                {
+                    var awaitableResult = function();
+                    if (awaitableResult != null)
+                    {
+                        var result = await awaitableResult.ConfigureAwait(false);
+                        taskCompletionSource.SetResult(result);
+                    }
+                    else
+                    {
+                        taskCompletionSource.SetException(new InvalidOperationException("The Task returned by function cannot be null."));
+                    }
+                }
+                catch (Exception e)
+                {
+                    taskCompletionSource.SetException(e);
+                }
+            });
 
             return taskCompletionSource.Task;
         }
@@ -194,12 +188,35 @@ public static Task<T> AwaitableRunAsync<T>(this CoreDispatcher dispatcher, Func<
         /// <returns>Awaitable Task</returns>
         public static Task AwaitableRunAsync(this CoreDispatcher dispatcher, Func<Task> function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
-            return dispatcher.AwaitableRunAsync<object>(
-                async () =>
+            if (function == null)
             {
-                await function().ConfigureAwait(false);
-                return null;
-            }, priority);
+                throw new ArgumentNullException("function can't be null!");
+            }
+
+            var taskCompletionSource = new TaskCompletionSource<object>();
+
+            var ignored = dispatcher.RunAsync(priority, async () =>
+            {
+                try
+                {
+                    var awaitableResult = function();
+                    if (awaitableResult != null)
+                    {
+                        await awaitableResult.ConfigureAwait(false);
+                        taskCompletionSource.SetResult(null);
+                    }
+                    else
+                    {
+                        taskCompletionSource.SetException(new InvalidOperationException("The Task returned by function cannot be null."));
+                    }
+                }
+                catch (Exception e)
+                {
+                    taskCompletionSource.SetException(e);
+                }
+            });
+
+            return taskCompletionSource.Task;
         }
 
         /// <summary>
@@ -217,7 +234,7 @@ public static Task<T> AwaitableRunAsync<T>(this CoreDispatcher dispatcher, Func<
                 throw new ArgumentNullException("function can't be null!");
             }
 
-            TaskCompletionSource<T> taskCompletionSource = new TaskCompletionSource<T>();
+            var taskCompletionSource = new TaskCompletionSource<T>();
 
             var ignored = dispatcher.RunAsync(priority, () =>
             {
@@ -243,11 +260,11 @@ public static Task<T> AwaitableRunAsync<T>(this CoreDispatcher dispatcher, Func<
         /// <returns>Awaitable Task</returns>
         public static Task AwaitableRunAsync(this CoreDispatcher dispatcher, Action function, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
         {
-            return dispatcher.AwaitableRunAsync<object>(
+            return dispatcher.AwaitableRunAsync(
                 () =>
                 {
                     function();
-                    return null;
+                    return (object)null;
                 }, priority);
         }
     }

docs/helpers/DispatcherHelper.md

@@ -1,10 +1,11 @@
 # DispatcherHelper
 
-The DispatcherHelper class enables easy interaction with [CoreDispatcher](https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.core.coredispatcher.aspx), mainly in the case of executing a block of code in UI thread from a non-UI thread.
+The DispatcherHelper class enables easy interaction with [CoreDispatcher](https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.core.coredispatcher.aspx), mainly in the case of executing a block of code on the UI thread from a non-UI thread.
 
 _What is included in the helper?_
 - Extension method with overloads for [CoreDispatcher](https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.core.coredispatcher.aspx) class.
-- Static helper methods of executing a specific function in UI thread current application's main window (configu)
+- Extension method with overloads for [CoreApplicationView](https://msdn.microsoft.com/en-us/library/windows/apps/windows.applicationmodel.core.coreapplicationview.aspx) (for multi window applications).
+- Static helper methods for executing a specific function on the UI thread of the current application's main window.
 
 
 ## Example
@@ -14,7 +15,7 @@ _What is included in the helper?_
     // Executing from a non-UI thread with helper method
      int returnedFromUIThread = await DispatcherHelper.ExecuteOnUIThreadAsync<int>(() =>
      {
-         // Code to execute with UI thread
+         // Code to execute on main window's UI thread
          NormalTextBlock.Text = "Updated from a random thread!";
          return 1;
      });
@@ -39,5 +40,5 @@ _What is included in the helper?_
 
 ## API
 
-* [Connection Helper source code](https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp/Helpers/DispatcherHelper.cs)
+* [DispatcherHelper source code](https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp/Helpers/DispatcherHelper.cs)