fix: changed order of calls in ContentDialog Hide complete handler to…

… invoke the closed handler before the result is set, and modified UI test to change the text before deferral is completed.

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Controls/ContentDialogTests/ContentDialog_Closing.xaml.cs

@@ -58,14 +58,14 @@ private void DeferredDialog_Click(object sender, RoutedEventArgs args)
 			var defer1Button = new _Button { Name = "Complete1Button", Content = "Complete 1" };
 			defer1Button.Click += (o, e) =>
 			{
-				deferral1.Complete();
 				ResultTextBlock.Text = "First complete called";
+				deferral1.Complete();
 			};
 			var defer2Button = new _Button { Name = "Complete2Button", Content = "Complete 2" };
 			defer2Button.Click += (o, e) =>
 			{
-				deferral2.Complete();
 				ResultTextBlock.Text = "Second complete called";
+				deferral2.Complete();
 			};
 			var panel = new StackPanel
 			{

src/Uno.UI/UI/Xaml/Controls/ContentDialog/ContentDialog.cs

@@ -125,9 +125,8 @@ void Complete(ContentDialogClosingEventArgs args)
 					_popup.IsOpen = false;
 					_popup.Child = null;
 					UpdateVisualState();
-					_tcs.SetResult(result);
-
 					Closed?.Invoke(this, new ContentDialogClosedEventArgs(result));
+					_tcs.SetResult(result);
 				}
 			}
 			var closingArgs = new ContentDialogClosingEventArgs(Complete, result);