Problems using inheritance with drag and drop in WPF

I have a usercontrol that I want to implement a drag and drop interface on, here are the vital parts of the implementation, and this works fine:

XML-file to the usercontrol to be draggable:

<UserControl 
         ...default xmlns...
         MouseLeftButtonDown="Control_MouseLeftButtonDown">
         ...GUI-ELEMENTS in the control...
</UserControl>

Code behind:

public partial class DragableControl : UserControl
{
    private void Control_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
         DragDrop.DoDragDrop(this, this, DragDropEffects.Move);
    }
}

XML-file to the usercontrol which will be able to accept a drag and drop operation:

<Usercontrol 
         ...default xmlns...>
    <Grid AllowDrop="True" Drop="Grid_Drop">
         ... GUI elements in the grid....
    </Grid> 
</Usercontrol>

Code behind:

public partial class DropClass: UserControl
{
    private void Grid_Drop(object sender, DragEventArgs e)
    {
        var control = (DragableControl)e.Data.GetData(typeof(DragableControl));
        if(control != null)
        {
            //do something
        }        
    }
}

To be able to create different usercontrols which have drag and drop functionality, I creates a base class, BaseDragableUserControl, which at the moment contains nothing, but inherits from usercontrol.

Code:

public class BaseDragableUserControl: UserControl
{
}

I change my code (both xaml and code):

 public partial class DragableControl : UserControl

I also changes the class for receiving to this:

public partial class DropClass: UserControl
{
    private void Grid_Drop(object sender, DragEventArgs e)
    {
        var control =(BaseDragableUserControl)e.Data.GetData(typeof(BaseDragableUserControl));
        if(control != null)
        {
            //do something
        }        
    }
}

But the control variable is always Null. I guess that the getdata in the DragEventsArgs does 开发者_开发百科not like inheritance. Is there a way to achieve this? To make it possible to use a base class for a drag and drop class?

Instead of passing this when you initiate the drag/drop, create one of the standard containers for that purpose. Specifically:

DragDrop.DoDragDrop(this, new DataObject("myFormat", this), DragDropEffects.Move);

and then now you know to expect a specific kind of data:

var control =(BaseDragableUserControl)e.Data.GetData("myFormat");