title: Position of dragged&dropped element (MouseDragElementBehavior)
body: <p>I'm trying to implement a WPF application with drag&amp;drop functionality using MouseDragElementBehavior.
  But I just can't find a way to get the dropped elements position relative to its parent Canavs.
  Example code:</p>
  
  <pre><code>namespace DragTest {
      public partial class MainWindow : Window {
  
          private Canvas _child;
  
          public MainWindow() {
              InitializeComponent();
  
              Canvas parent = new Canvas();
              parent.Width = 400;
              parent.Height = 300;
              parent.Background = new SolidColorBrush(Colors.LightGray);    
  
              _child = new Canvas();
              _child.Width = 50;
              _child.Height = 50;
              _child.Background = new SolidColorBrush(Colors.Black);
  
              MouseDragElementBehavior dragBehavior = new MouseDragElementBehavior();
              dragBehavior.Attach(_child);
              dragBehavior.DragBegun += onDragBegun;
              dragBehavior.DragFinished += onDragFinished;
  
              Canvas.SetLeft(_child, 0);
              Canvas.SetTop(_child, 0);
  
              parent.Children.Add(_child);
  
              Content = parent;
  
          }
  
          private void onDragBegun(object sender, MouseEventArgs args) {
              Debug.WriteLine(Canvas.GetLeft(_child));
          }
  
          private void onDragFinished(object sender, MouseEventArgs args) {
              Debug.WriteLine(Canvas.GetLeft(_child));
          }
      }
  }
  </code></pre>
  
  <p>After Dropping the child Canvas the value of <code>Canvas.GetLeft(_child)</code> is still 0.
  Why that? Why doesn't it change?</p>
  
  <p>Sure, I can get the new position by using <code>dragBehavior.X</code>, but that's the child Canvas' position in the main window, not the position relative to the parent Canvas. There must be a way to get it...</p>