由於ContextMenu不繼承父級的DataContext，所以如果要綁定父級的DataContext，直接DataContext=“{Binding}”是行不通的。因此可通過以下兩個方式解決綁定的問題。

1、使用資源的方式

 1         <Button Content="Test" Command="{Binding TestCommand}">
 2             <Button.Resources>
 3                 <vm:ThreeViewModel 
 
x:Key="Three"/>
 4             </Button.Resources>
 5             <Button.ContextMenu>
 6                 <ContextMenu>
 7                     <MenuItem Header="測試" Command="{Binding TestCommand,Source={StaticResource Three}}"/>
 8                 </ContextMenu>
 9
 
             </Button.ContextMenu>
10         </Button>
11     

2、利用ContextMenu的PlacementTarget屬性

        <Button Content="Test" Command="{Binding TestCommand}">
            <Button.ContextMenu>
                <ContextMenu>
                    <MenuItem Header
 
="測試" Command="{Binding PlacementTarget.DataContext.TestCommand,  RelativeSource={RelativeSource AncestorType=ContextMenu} }"/>
                </ContextMenu>
            </Button.ContextMenu>
        </Button>

MVVM 下 ContextMenu的命令綁定