wpf中listbox外边框,无论怎么设置都无法显示出来,不知道怎么解决。
```c#
<ListBox x:Name="listbox" Margin="323,65,616,307" BorderThickness="2" BorderBrush="Black" >
<ListBox.Template>
<ControlTemplate TargetType="{x:Type ListBox}">
<ScrollViewer HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
<WrapPanel Orientation="Horizontal" IsItemsHost="True" ScrollViewer.CanContentScroll="True"/>
</ScrollViewer>
</ControlTemplate>
</ListBox.Template>
</ListBox>
```