WPF ContextMenu 在MVVM模式中无法绑定 Command的解决办法

ContextMenu无论定义在.cs或.xaml文件中，都不继承父级的DataContext，所以如果要绑定父级的DataContext，直接DataContext=“{Binding}”是行不通的

不能绑父级，但是能绑资源

第一步：定义一个中间类用来做资源对象

 1 public class BindingProxy : Freezable
 2     {
 3         #region Overrides of Freezable
 4
 5         protected override Freezable CreateInstanceCore()
 6         {
 7             return new BindingProxy();
 8         }
 9
10         #endregion
11
12         public object Data
13         {
14             get { return (object)GetValue(DataProperty); }
15             set { SetValue(DataProperty, value); }
16         }
17
18         public static readonly DependencyProperty DataProperty =
19             DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
20     }

第二步：引用命名空间，在控件中定义资源

1 <UserControl.Resources>
2         <libBinding:BindingProxy x:Key="BindingProxy" Data="{Binding}"/>
3     </UserControl.Resources>

第三步：绑定ContextMenu、MenuItem

（Button.Command 和 ContextMenu.IsOpen 的绑定部分可以不关注，这两个绑定是用来控制ContextMenu打开的）

 1 <Button Command="{Binding Customfold}">
 2             <Button.ContextMenu>
 3                 <ContextMenu DataContext="{Binding Data,Source={StaticResource BindingProxy}}"
 4                              ItemsSource="{Binding ItemModelCollection}"
 5                              IsOpen="{Binding OpenCustomfold,Mode=OneWay}">
 6                     <ContextMenu.ItemContainerStyle>
 7                         <Style TargetType="MenuItem">
 8                             <Setter Property="Header" Value="{Binding ...}"/>
 9                             <Setter Property="Command" Value="{Binding ...}"/>
10                             <Setter Property="CommandParameter" Value="{Binding ...}"/>
11                         </Style>
12                     </ContextMenu.ItemContainerStyle>
13                 </ContextMenu>
14             </Button.ContextMenu>
15             <Image .../>
16         </Button>

参考：

http://www.thomaslevesque.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-inherited/

http://stackoverflow.com/questions/1580753/wpf-contextmenu-with-itemssource-how-to-bind-to-command-in-each-item