0down votefavorite

am trying to do a drag and drop of an expander from the lisbox "faire" to the listbox "cours" using this code:

 
 
private void faire_MouseUp(object sender, MouseButtonEventArgs e)
{
ListBoxItem i = sender as ListBoxItem;
DataObject data = new DataObject(typeof(ListBoxItem));
DragDropEffects dde1 = DragDrop.DoDragDrop(_dragged, data, DragDropEffects.Move);
}

private void faire_MouseDown(object sender, MouseButtonEventArgs e)
{
ListBoxItem i = sender as ListBoxItem;
DataObject data = new DataObject(typeof(ListBoxItem), i);
DragDropEffects dde1 = DragDrop.DoDragDrop(_dragged, data, DragDropEffects.Move);
}

private void cours_DragEnter(object sender, DragEventArgs e)
{
if (_dragged == null)
e.Effects = DragDropEffects.None;
else
e.Effects = DragDropEffects.All;
}

private void cours_Drop(object sender, DragEventArgs e)
{
ListBox parent = (ListBox)sender;
object data = e.Data.GetData(typeof(Expander));
faire.Items.Remove(data);
parent.Items.Add(data);
}

private void faire_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
ListBox parent = (ListBox)sender;
dragSource = parent;
object data = GetDataFromListBox(dragSource, e.GetPosition(parent));

if (data != null)
{
DragDrop.DoDragDrop(parent, data, DragDropEffects.Move);
}
}
#region GetDataFromListBox(ListBox,Point)
private static object GetDataFromListBox(ListBox source, Point point)
{
UIElement element = source.InputHitTest(point) as UIElement;
if (element != null)
{
object data = DependencyProperty.UnsetValue;
while (data == DependencyProperty.UnsetValue)
{
data = source.ItemContainerGenerator.ItemFromContainer(element);
if (data == DependencyProperty.UnsetValue)
{
element = VisualTreeHelper.GetParent(element) as UIElement;
}
if (element == source)
{
return null;
}
}
if (data != DependencyProperty.UnsetValue)
{
return data;
}
}
return null;
}

#endregion
 
 
the drag is working but i cant expand the expander anymore what should i do ? 
`