title: gong-wpf-dragdrop on different type of observablecollection
body: <p>let say I have two ObservableCollection on my WPF app.</p>
  
  <p>I need to drag one list of type "Module"</p>
  
  <pre><code>ObservableCollection&lt;IModuleInfo&gt; Modules
  </code></pre>
  
  <p>into a list of type "task"</p>
  
  <pre><code>ObservableCollection&lt;TaskInfo&gt; Tasks
  </code></pre>
  
  <p>if module is being dropped into task list, i will do  a conversion of module into task first, and then add the new task on the list.</p>
  
  <p>i use gong-wpf-dragdrop, the default adorner is good. 
  how do i do this? can't find the solution elsewhere.</p>
  
  <pre><code>&lt;ItemsControl Grid.Row="1" ItemsSource="{Binding Modules}" 
  dd:DragDrop.IsDragSource="True"
  dd:DragDrop.IsDropTarget="False"
  dd:DragDrop.UseDefaultDragAdorner="True"&gt;
      &lt;ItemsControl.ItemsPanel&gt;
      &lt;ItemsPanelTemplate&gt;
      &lt;UniformGrid Columns="1" /&gt;
      &lt;/ItemsPanelTemplate&gt;
      &lt;/ItemsControl.ItemsPanel&gt;
      &lt;ItemsControl.ItemTemplate&gt;
      &lt;DataTemplate&gt;
      &lt;Grid Margin="5"&gt;
      &lt;/Grid&gt;
      &lt;/DataTemplate&gt;
      &lt;/ItemsControl.ItemTemplate&gt;                      
  &lt;/ItemsControl&gt;
  </code></pre>
  
  <p>the drop target will be:</p>
  
  <pre><code>&lt;ItemsControl Grid.Row="1" Margin="0,0,0,0"                                                          dd:DragDrop.IsDragSource="False"
  dd:DragDrop.IsDropTarget="True"                                                    dd:DragDrop.UseDefaultDragAdorner="True"
  dd:DragDrop.DropHandler="{Binding}"                                    
  ItemsSource="{Binding Tasks}"
  &gt;
  
      &lt;ItemsControl.ItemsPanel&gt;
      &lt;ItemsPanelTemplate&gt;
      &lt;StackPanel Orientation="Vertical" /&gt;
      &lt;/ItemsPanelTemplate&gt;
      &lt;/ItemsControl.ItemsPanel&gt;
      &lt;ItemsControl.ItemTemplate&gt;
      &lt;DataTemplate&gt;
      &lt;Grid&gt; &lt;/Grid&gt;
  &lt;/ItemsControl&gt;
  </code></pre>
  
  <p>I have implemented the IDropTarget on the view model,</p>
  
  <p>but it seems like the  </p>
  
  <pre><code>public void Drop(IDropInfo dropInfo)
      {
  </code></pre>
  
  <p>won't accept a different types of object on drop.</p>