HierarchicalDataTemplate中的ContextMenu的Command绑定

<ContextMenu x:Key="ModeMenu">
            <MenuItem Header="添加" Command="{Binding AddCommand}"
                      CommandParameter="{Binding ElementName=ModesTree, Path=SelectedItem}">
                <MenuItem.Icon>
                    <Image Source="../Images/Add.png" Width="16" Height="16" />
                </MenuItem.Icon>
            </MenuItem>
        </ContextMenu>

<HierarchicalDataTemplate x:Key="ModeTemplate" DataType="{x:Type Model:ModeInfo}" ItemsSource="{Binding Path=PlanInfoList}" > 
            <StackPanel Orientation="Horizontal" ContextMenu="{StaticResource ModeMenu}" 
                        DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}">
                <Image x:Name="imgStatus" Source="../Images/Add.png" Width="16" Height="16" />
                <TextBlock Margin="2,0,0,0" VerticalAlignment="Center" FontWeight="Bold" Text="{Binding ModeName}"  />
            </StackPanel>
        </HierarchicalDataTemplate>

如代码所示，这个MenuItem的Command并不起作用。网上有人给出的解释是：ContentMenu是作为你一个popup的窗口出现在UI上的，因此，这个Popup和原来的窗口并不是同一个VisualTree，既然不在同一个VisualTree中，则无法找到DataContext。

解决方法如下：

定义一个类CommandReference：

public class CommandReference : Freezable, ICommand, ICommandSource
    {
        public CommandReference()
        {
            
        }

        public static readonly DependencyProperty CommandParameterProperty =
          DependencyProperty.Register(
              "CommandParameter",
              typeof(object),
              typeof(CommandReference),
              new PropertyMetadata((object)null));

        public object CommandParameter
        {
            get
            {
                return (object)GetValue(CommandParameterProperty);
            }
            set
            {
                SetValue(CommandParameterProperty, value);
            }
        }

        public static readonly DependencyProperty CommandTargetProperty =
           DependencyProperty.Register(
               "CommandTarget",
               typeof(IInputElement),
               typeof(CommandReference),
               new PropertyMetadata((IInputElement)null));

        public IInputElement CommandTarget
        {
            get
            {
                return (IInputElement)GetValue(CommandTargetProperty);
            }
            set
            {
                SetValue(CommandTargetProperty, value);
            }
        } 

        public static readonly DependencyProperty CommandProperty = DependencyProperty.Register("Command", typeof(ICommand), typeof(CommandReference), new PropertyMetadata(new PropertyChangedCallback(OnCommandChanged)));

        public ICommand Command
        {
            get { return (ICommand)GetValue(CommandProperty); }
            set { SetValue(CommandProperty, value); }
        }

        #region ICommand Members

        public bool CanExecute(object parameter)
        {
            if (Command != null)
                return Command.CanExecute(CommandParameter);
            return false;
        }

        public void Execute(object parameter)
        {
            Command.Execute(CommandParameter);
        }

        public event EventHandler CanExecuteChanged;

        private static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            CommandReference commandReference = d as CommandReference;
            ICommand oldCommand = e.OldValue as ICommand;
            ICommand newCommand = e.NewValue as ICommand;

            if (oldCommand != null)
            {
                oldCommand.CanExecuteChanged -= commandReference.CanExecuteChanged;
            }
            if (newCommand != null)
            {
                newCommand.CanExecuteChanged += commandReference.CanExecuteChanged;
            }
        }

        #endregion

        #region Freezable

        protected override Freezable CreateInstanceCore()
        {
            throw new NotImplementedException();
        }

        #endregion
    }

然后修改View中的代码，先插入一个CommandReference资源，将其绑定到命令，再将菜单的命令绑定到资源，如下所示：

<UserControl.Resources>
<c:CommandReference x:Key="AddModeCommandRef" Command="{Binding Path=AddModeCommand}"/>
<ContextMenu x:Key="RootMenu" >
            <MenuItem Header="添加" Command="{StaticResource AddModeCommandRef}" >                
                <MenuItem.Icon>
                    <Image Source="../Images/Add.png" Width="16" Height="16" />
                </MenuItem.Icon>
            </MenuItem>
        </ContextMenu>
<HierarchicalDataTemplate x:Key="ModeTemplate" DataType="{x:Type Model:ModeInfo}" ItemsSource="{Binding Path=PlanInfoList}" >
            <StackPanel Orientation="Horizontal" ContextMenu="{StaticResource ModeMenu}" DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}">                 <Image x:Name="imgStatus" Source="../Images/Add.png" Width="16" Height="16" />
                <TextBlock Margin="2,0,0,0" VerticalAlignment="Center" FontWeight="Bold" Text="{Binding ModeName}" />
            </StackPanel>
        </HierarchicalDataTemplate>

最后在ViewModel中定义命令即可：

public ICommand AddModeCommand { get; set; }

参考文章：

http://social.msdn.microsoft.com/Forums/zh-SG/wpfzhchs/thread/13bcc6e4-d3f7-40c8-a9e8-ee35918edc14

http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/36ce07fc-64de-4dc9-8012-3c4f03605c30/