while dragging, I don't see helper-lines in Silverlight

问题

Silverlight 4, Toolkit

During dragging an item on TARGET CONTROL, there are NOT visible lines showing (during mouse move) actual position where will be dragged item put on

(for example, between items, inside item, before item, …)

source control

    <toolkit:ListBoxDragDropTarget AllowDrop="False" AllowedSourceEffects="Copy, Link, Scroll">
      <ListBox ItemsSource="{Binding ToolboxItems}">
             <ListBox.ItemTemplate>
                 <DataTemplate> <!-- some binding --> </DataTemplate>
           </ListBox.ItemTemplate>   
      </ListBox>
   </toolkit:ListBoxDrag...>

target control

<toolkit:TreeViewDragDropTarget AllowDrop="True">
   <sdk:TreeView ItemsSource="{Binding ScriptRows}"  
     <sdk:TreeView.ItemTemplate>
      <sdk:HierarchicalDataTemplate ItemsSource="{Binding Path=Children}">
         <!-- some binding -->
     </sdk:HierarchicalDataTemplate>
   </sdk:TreeView.ItemTemplate>
</sdk:TreeView>

Can somebody help me and say what's wrong ? Thank you

回答1:

Ok, it's because the source type MUST be the same interface (type) as TARGET

来源：https://stackoverflow.com/questions/4286522/while-dragging-i-dont-see-helper-lines-in-silverlight