Improved codegen, removed unnecessary allocations

The previous version caused the C# compiler to always instantiate a display class for the closure even if the execution had thread access

Author: Sergio0694

Microsoft.Toolkit.Uwp/Helpers/DispatcherQueueHelper.cs

@@ -43,23 +43,28 @@ public static Task ExecuteOnUIThreadAsync(this DispatcherQueue dispatcher, Actio
                 }
             }
 
-            var taskCompletionSource = new TaskCompletionSource<object>();
-
-            _ = dispatcher.TryEnqueue(priority, () =>
+            static Task RunAsync(DispatcherQueue dispatcher, Action function, DispatcherQueuePriority priority)
             {
-                try
-                {
-                    function();
+                var taskCompletionSource = new TaskCompletionSource<object>();
 
-                    taskCompletionSource.SetResult(null);
-                }
-                catch (Exception e)
+                _ = dispatcher.TryEnqueue(priority, () =>
                 {
-                    taskCompletionSource.SetException(e);
-                }
-            });
+                    try
+                    {
+                        function();
+
+                        taskCompletionSource.SetResult(null);
+                    }
+                    catch (Exception e)
+                    {
+                        taskCompletionSource.SetException(e);
+                    }
+                });
 
-            return taskCompletionSource.Task;
+                return taskCompletionSource.Task;
+            }
+
+            return RunAsync(dispatcher, function, priority);
         }
 
         /// <summary>
@@ -87,21 +92,26 @@ public static Task<T> ExecuteOnUIThreadAsync<T>(this DispatcherQueue dispatcher,
                 }
             }
 
-            var taskCompletionSource = new TaskCompletionSource<T>();
-
-            _ = dispatcher.TryEnqueue(priority, () =>
+            static Task<T> RunAsync(DispatcherQueue dispatcher, Func<T> function, DispatcherQueuePriority priority)
             {
-                try
-                {
-                    taskCompletionSource.SetResult(function());
-                }
-                catch (Exception e)
+                var taskCompletionSource = new TaskCompletionSource<T>();
+
+                _ = dispatcher.TryEnqueue(priority, () =>
                 {
-                    taskCompletionSource.SetException(e);
-                }
-            });
+                    try
+                    {
+                        taskCompletionSource.SetResult(function());
+                    }
+                    catch (Exception e)
+                    {
+                        taskCompletionSource.SetException(e);
+                    }
+                });
 
-            return taskCompletionSource.Task;
+                return taskCompletionSource.Task;
+            }
+
+            return RunAsync(dispatcher, function, priority);
         }
 
         /// <summary>
@@ -137,30 +147,35 @@ public static Task ExecuteOnUIThreadAsync(this DispatcherQueue dispatcher, Func<
                 }
             }
 
-            var taskCompletionSource = new TaskCompletionSource<object>();
-
-            _ = dispatcher.TryEnqueue(priority, async () =>
+            static Task RunAsync(DispatcherQueue dispatcher, Func<Task> function, DispatcherQueuePriority priority)
             {
-                try
+                var taskCompletionSource = new TaskCompletionSource<object>();
+
+                _ = dispatcher.TryEnqueue(priority, async () =>
                 {
-                    if (function() is Task awaitableResult)
+                    try
                     {
-                        await awaitableResult.ConfigureAwait(false);
-
-                        taskCompletionSource.SetResult(null);
+                        if (function() is Task awaitableResult)
+                        {
+                            await awaitableResult.ConfigureAwait(false);
+
+                            taskCompletionSource.SetResult(null);
+                        }
+                        else
+                        {
+                            taskCompletionSource.SetException(new InvalidOperationException("The Task returned by function cannot be null."));
+                        }
                     }
-                    else
+                    catch (Exception e)
                     {
-                        taskCompletionSource.SetException(new InvalidOperationException("The Task returned by function cannot be null."));
+                        taskCompletionSource.SetException(e);
                     }
-                }
-                catch (Exception e)
-                {
-                    taskCompletionSource.SetException(e);
-                }
-            });
+                });
 
-            return taskCompletionSource.Task;
+                return taskCompletionSource.Task;
+            }
+
+            return RunAsync(dispatcher, function, priority);
         }
 
         /// <summary>
@@ -193,30 +208,35 @@ public static Task<T> ExecuteOnUIThreadAsync<T>(this DispatcherQueue dispatcher,
                 }
             }
 
-            var taskCompletionSource = new TaskCompletionSource<T>();
-
-            _ = dispatcher.TryEnqueue(priority, async () =>
+            static Task<T> RunAsync(DispatcherQueue dispatcher, Func<Task<T>> function, DispatcherQueuePriority priority)
             {
-                try
+                var taskCompletionSource = new TaskCompletionSource<T>();
+
+                _ = dispatcher.TryEnqueue(priority, async () =>
                 {
-                    if (function() is Task<T> awaitableResult)
+                    try
                     {
-                        var result = await awaitableResult.ConfigureAwait(false);
-
-                        taskCompletionSource.SetResult(result);
+                        if (function() is Task<T> awaitableResult)
+                        {
+                            var result = await awaitableResult.ConfigureAwait(false);
+
+                            taskCompletionSource.SetResult(result);
+                        }
+                        else
+                        {
+                            taskCompletionSource.SetException(new InvalidOperationException("The Task returned by function cannot be null."));
+                        }
                     }
-                    else
+                    catch (Exception e)
                     {
-                        taskCompletionSource.SetException(new InvalidOperationException("The Task returned by function cannot be null."));
+                        taskCompletionSource.SetException(e);
                     }
-                }
-                catch (Exception e)
-                {
-                    taskCompletionSource.SetException(e);
-                }
-            });
+                });
+
+                return taskCompletionSource.Task;
+            }
 
-            return taskCompletionSource.Task;
+            return RunAsync(dispatcher, function, priority);
         }
     }
 }

Microsoft.Toolkit.Uwp/Microsoft.Toolkit.Uwp.csproj

@@ -5,6 +5,7 @@
     <Title>Windows Community Toolkit</Title>
     <Description>This package includes code only helpers such as Colors conversion tool, Storage file handling, a Stream helper class, etc.</Description>
     <PackageTags>UWP Toolkit Windows</PackageTags>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>