How to capture Mouse Down event outside a control?

Question

Mouse Capture doesn't work:
public partial class MainWindow : Window
public MainWindow()
InitializeComponent();
Button button1 = new Button();
button1.Width = 50;
button1.Height = 20;
this.Content = button1;
Mouse.Capture(button1);
button1.PreviewMouseDown += Down;
private void Down(object sender, MouseButtonEventArgs e)
MessageBox.Show("Hello World!"); // doesn't show

Answer 1

Hi Ziya,
the Capture-method returns a bool whether the capture was successful or not. So when you do this, you'll see that your capture didn't work:
public MainWindow()
InitializeComponent();
Button button1 = new Button();
button1.Width = 50;
button1.Height = 20;
this.Content = button1;
var success = Mouse.Capture(button1);
if(!success)
MessageBox.Show("Not captured");
button1.PreviewMouseDown += Down;
The problem with the code above is that your Window is not loaded at that time when the code in the constructor is executed. And as long as it is not loaded, there's nothing to capture. :-)
So you should do your capture-logic in the Loaded-event of the window. That event occurs after the Window has been loaded. So the code below will work for you:
public MainWindow()
InitializeComponent();
Button button1 = new Button();
button1.Width = 50;
button1.Height = 20;
this.Content = button1;
this.Loaded += (s, e) =>
var success = Mouse.Capture(button1);
if (!success)
MessageBox.Show("Not captured");
button1.PreviewMouseDown += Down;
Thomas Claudius Huber
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