#729 – Mouse.GetPosition Doesn’t Work While Dragging

If you are handling the DragOver event during a drag-and-drop operation and you want to find the current mouse position, you need to use DragEventArgs.GetPosition, rather than the static Mouse.GetPosition method.

In the example below, we initiate a drag-and-drop operation in a window and then try reporting the mouse’s position in the window’s DragOver handler.  We try using both methods to get the mouse position, but only the DragEventArgs.GetPosition method works.

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Application 2" Height="350" Width="325"
        MouseDown="Window_MouseDown"
        AllowDrop="True" DragOver="Window_DragOver">
    <StackPanel>
        <Label Name="lblInfo1" Content="Info 1"/>
        <Label Name="lblInfo2" Content="Info 2"/>
    </StackPanel>
</Window>

 

        private void Window_MouseDown(object sender, MouseButtonEventArgs e)
        {
            DragDrop.DoDragDrop((DependencyObject)e.Source, "Sample", DragDropEffects.Copy);
        }

        private void Window_DragOver(object sender, DragEventArgs e)
        {
            System.Windows.Point p1 = Mouse.GetPosition(this);
            lblInfo1.Content = string.Format("Mouse.GetPosition: {0}, {1}", p1.X, p1.Y);

            System.Windows.Point p2 = e.GetPosition(this);
            lblInfo2.Content = string.Format("DragEventArgs.GetPosition: {0}, {1}", p2.X, p2.Y);
        }

729-001

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About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

2 Responses to #729 – Mouse.GetPosition Doesn’t Work While Dragging

  1. Pingback: Dew Drop – January 9, 2013 (#1,477) | Alvin Ashcraft's Morning Dew

  2. benlitz says:

    The GetPosition method is pretty broken when invoked from the DragLeave handler. Here’s an old post (not from me) describing the problem: https://social.msdn.microsoft.com/Forums/vstudio/en-US/d326384b-e182-4f48-ab8b-841a2c2ca4ab/whats-up-with-dragleave-and-egetposition?forum=wpf

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