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Control.MouseCaptureChanged Event

Occurs when the control loses mouse capture.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public event EventHandler MouseCaptureChanged

In rare scenarios, you might need to detect unexpected input. For example, consider the following scenarios.

  • During a mouse operation, the user opens the Start menu by pressing the Windows key or CTRL+ESC.

  • During a mouse operation, the user switches to another program by pressing ALT+TAB.

  • During a mouse operation, another program displays a window or a message box that takes focus away from the current application.

Mouse operations can include clicking and holding the mouse on a form or a control, or performing a mouse drag operation. If you have to detect when a form or a control loses mouse capture for these and related unexpected scenarios, you can use the MouseCaptureChanged event.

The following code example demonstrates the MouseCaptureChanged event for a Button control.

private void button1_MouseDown(object sender, MouseEventArgs e)
{
    System.Diagnostics.Debug.WriteLine("button1_MouseDown");
}

private void button1_MouseUp(object sender, MouseEventArgs e)
{
    System.Diagnostics.Debug.WriteLine("button1_MouseUp");
}

private void button1_MouseCaptureChanged(object sender, EventArgs e)
{
    System.Diagnostics.Debug.WriteLine("button1_MouseCaptureChanged");
}

To test this example, run it in the debugger by pressing F5. Open the Output window in Visual Studio so that you can see when events are raised. Click the Button and notice the following output.

button1_MouseDown

button1_MouseUp

button1_MouseCaptureChanged

Now, click and hold the left mouse button on the Button control. While still clicking the mouse, press ALT+TAB to switch to another program. Notice that the MouseCaptureChanged event is raised enabling you to potentially handle this scenario. Depending on your actions, the MouseUp event might not be raised. You can also try this test with the Windows key or CTRL+ESC.

button1_MouseDown

button1_MouseCaptureChanged

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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