Where is the Application.DoEvents() in WPF?

Question

I have the following sample code that zooms each time a button is pressed:

XAML:

<Window x:Class="WpfApplication12.MainWindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         Title="MainWindow" Height="350" Width="525">      <Canvas x:Name="myCanvas">          <Canvas.LayoutTransform>             <ScaleTransform x:Name="myScaleTransform" />         </Canvas.LayoutTransform>           <Button Content="Button"                  Name="myButton"                  Canvas.Left="50"                  Canvas.Top="50"                  Click="myButton_Click" />     </Canvas> </Window> 

*.cs

public partial class MainWindow : Window {     public MainWindow()     {         InitializeComponent();     }      private void myButton_Click(object sender, RoutedEventArgs e)     {         Console.WriteLine("scale {0}, location: {1}",              myScaleTransform.ScaleX,             myCanvas.PointToScreen(GetMyByttonLocation()));          myScaleTransform.ScaleX =             myScaleTransform.ScaleY =             myScaleTransform.ScaleX + 1;                  Console.WriteLine("scale {0}, location: {1}",             myScaleTransform.ScaleX,             myCanvas.PointToScreen(GetMyByttonLocation()));     }          private Point GetMyByttonLocation()     {         return new Point(             Canvas.GetLeft(myButton),             Canvas.GetTop(myButton));     } } 

the output is:

scale 1, location: 296;315 scale 2, location: 296;315  scale 2, location: 346;365 scale 3, location: 346;365  scale 3, location: 396;415 scale 4, location: 396;415 

as you can see, there is a problem, that I thought solve by using Application.DoEvents(); but... it does not exist a priori in .NET 4.

What to do?

Answer 1

Try something like this

public static void DoEvents() {     Application.Current.Dispatcher.Invoke(DispatcherPriority.Background,                                           new Action(delegate { })); } 

Answer 2

Well, I just hit a case where I start work on a method that runs on the Dispatcher thread, and it needs to block without blocking the UI Thread. Turns out that msdn explains how to implement a DoEvents() based on the Dispatcher itself:

public void DoEvents() {     DispatcherFrame frame = new DispatcherFrame();     Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background,         new DispatcherOperationCallback(ExitFrame), frame);     Dispatcher.PushFrame(frame); }  public object ExitFrame(object f) {     ((DispatcherFrame)f).Continue = false;      return null; } 

(taken from Dispatcher.PushFrame Method)

Some may prefer it in a single method that will enforce the same logic:

public static void DoEvents() {     var frame = new DispatcherFrame();     Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background,         new DispatcherOperationCallback(             delegate (object f)             {                 ((DispatcherFrame)f).Continue = false;                 return null;             }),frame);     Dispatcher.PushFrame(frame); }