private void OnPlaceholderEnter(SpacerWrapper wrapper, DragEventArgs e)
 {
     if (!this.AllowDropOnSpacer(e))
     {
         return;
     }
     this.SpacerToShow = wrapper;
     this.SpacerTimer.Start();
     e.Handled = true;
 }
 private void OnPlaceholderEnter(SpacerWrapper wrapper, DragEventArgs e)
 {
     if (!this.AllowDropOnSpacer(e))
     {
         return;
     }
     this.SpacerToShow = wrapper;
     this.SpacerTimer.Start();
     e.Handled = true;
 }