How to capture Mouse Down event outside a control?

Question

1.50/5 (2 votes)

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Mouse Capture doesn't work:

C#

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
    }
}

Posted 25-Apr-15 21:39pm

Ziya1995

Updated 26-Apr-15 1:29am

v6

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Comments

Sergey Alexandrovich Kryukov 26-Apr-15 12:43pm

It does work. What did you try to achieve with that? Capturing a mouse in a constructor is absurd, of course.
—SA

2 solutions

Solution 1

Please see my comment to the question.

You are trying to capture the mouse to the element which is not even rendered. How could it possibly work? Mouse should be captured sometimes, but it should be done only temporarily, for relatively short period of time. For example, you can implement button-like behavior, if you capture mouse in its MouseDown event, to be able to handle a MouseUp event (for example), even when the mouse pointer goes out of the element's boundaries, but then the mouse should be un-captured in the handle on this second event immediately. This is just an example.

Please see:
https://msdn.microsoft.com/en-us/library/system.windows.uielement.capturemouse%28v=vs.110%29.aspx[^],
https://msdn.microsoft.com/en-us/library/system.windows.input.mouse.capture%28v=vs.110%29.aspx[^].

Read "Remarks" section thoroughly. Any questions?

—SA

Posted 26-Apr-15 6:50am

Sergey Alexandrovich Kryukov

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Ziya1995 · Accepted Answer · 2015-04-26T08:32:00

Replace your code by the next to get it working:

C#

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        Button button1 = new Button();
        button1.Width = 50;
        button1.Height = 20;

        this.Content = button1;

        this.Loaded += delegate { Mouse.Capture(button1); };
        button1.PreviewMouseDown += Down;
    }

    private void Down(object sender, MouseButtonEventArgs e)
    {
        MessageBox.Show("Hello World!"); // shows
    }
}