WinForms window drag event

Is there an event in WinForms that get's fired when a window is dragged?

Or is there a better way of doing what I want: to drop the window opacity to 80% when the window is being dragged around?

Unfortunately this is stupidly tricky to se开发者_高级运维arch for because everyone is looking for drag and drop from the shell, or some other object.

No need for WndProc hacking, this works fine:

protected override void OnResizeBegin(EventArgs e) {
  this.Opacity = 0.6;
}
protected override void OnResizeEnd(EventArgs e) {
  this.Opacity = 1.0;
}

Moves also trigger the OnResizeXxx events.

It's the LocationChanged event you want:

private void YourApp_LocationChanged(object sender, EventArgs e)
{
    this.Opacity = 0.8;
}

You'll have to override WndProc and handle the exit move event to reset the opacity back to 1:

protected override void WndProc(ref Message m)
{
    Trace.WriteLine(m.ToString());
    switch (m.Msg)
    {
        case WMEXITSIZEMOVE:
            this.Opacity = 1.0;
            break;
    }
    base.WndProc(ref m);
}

Not forgetting to define the message code:

private const int WMEXITSIZEMOVE = 0x0232;

It might be more efficient to handle the WM_ENTERSIZEMOVE (code 0x0231) message instead of LocationChanged as this would only result in setting the opacity once (at the start of the drag) rather than continually throughout the drag.