要怎么解决那个白色的边边?margin panding 都设置过了没用,应该需要修改 文件菜单的属性才行,但我不知道怎么修改
```xml
<Menu Grid.Column="1" BorderBrush="#505050" Background="#505050" BorderThickness="0">
<MenuItem Background="#505050" Header="文件" BorderThickness="0" >
<MenuItem Header="打开" Background="#505050" BorderThickness="0"/>
<MenuItem Header="保存" Background="#505050" BorderThickness="0" />
</MenuItem>
<MenuItem Header="选项" BorderThickness="0" Height="30">
</MenuItem>
<MenuItem Header="宏指令" BorderThickness="0" Height="30"/>
<MenuItem Header="工作区" BorderThickness="0" Height="30"/>
<MenuItem Header="帮助" BorderThickness="0" Height="30"/>
</Menu>
```