拖放不起作用？

Question

我尝试了所有方法（将网格背景设置为透明等）。我无法让它工作。

<Grid Margin="0,0,0,-9" Background="Transparent">

    <ListBox x:Name="PlaylistBox" 
             HorizontalAlignment="Left" VerticalAlignment="Top"
             Height="358" Margin="19,274,0,0" Width="299" 
             Grid.ColumnSpan="3" BorderThickness="0" 
             Foreground="White" Background="Black" 
             SelectionChanged="PlaylistBox_SelectionChanged" 
             MouseDoubleClick="PlaylistBox_MouseDoubleClick" 
             AllowDrop="True"  
             Drop="PlaylistBox_Drop"/>
</Grid>

我做错了什么？