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

The old Application.DoEvents() method has been deprecated in WPF in favor of using a Dispatcher or a Background Worker Thread to do the processing as you have described. See the links for a couple of articles on how to use both objects.

If you absolutely must use Application.DoEvents(), then you could simply import the system.windows.forms.dll into your application and call the method. However, this really isn’t recommended, since you’re losing all the advantages that WPF provides.