WPF里面Grid不能接受拖放操作吗？

鼠标拖进来显示的图标是不能接受拖放的，不知何故？必须要拖到内嵌的那个Label上才能接受拖放。    <Grid DragEnter="Grid_DragEnter" Drop="Grid_Drop" AllowDrop="True" Width="507" DragOver="Grid_DragOver">
        <ListBox Visibility="Hidden" Height="311" HorizontalAlignment="Left" Name="FileList" VerticalAlignment="Top" Width="507" />
        <Label Visibility="Visible" Content="Please drag folder here." Height="28" HorizontalAlignment="Center" Name="Lable" VerticalAlignment="Center" Width="141" />
    </Grid>
        private void Grid_DragEnter(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop))
            {
                e.Effects = DragDropEffects.Copy;
            }
            else
            {
                e.Effects = DragDropEffects.None;
            }
            e.Handled = true;
        }        private void Grid_DragOver(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop))
            {
                e.Effects = DragDropEffects.Copy;
            }
            else
            {
                e.Effects = DragDropEffects.None;
            }
            e.Handled = true;        }