如何从ItemTemplate内将命令绑定到ContextMenu？ [英] How to bind a Command to a ContextMenu from within an ItemTemplate?

问题描述

我想将某个命令绑定到 menuItem 。所述菜单项是 ContextTemplate 的一部分，该上下文菜单在 ItemTemplate 内定义。

I want to bind a certain command to a menuItem. The said menu item is part of a ContextMenu that is defined inside an ItemTemplate.

现在，我已经编译并运行了什么，但是从未调用过该命令。过去，我曾使用类似的模式将命令成功地链接到 ItemTemplate 中定义的按钮。

Right now, what I have compiles and runs, but the command is never called. In the past, I had used a similar pattern to hook commands to buttons defined in an ItemTemplate with success.

有人知道我该怎么做吗？

Anyone has any idea how I could accomplish this?

XAML：

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:Wpf_treeView" x:Name="window" x:Class="Wpf_treeView.MainWindow"
    Title="MainWindow" Height="350" Width="525">
  <Grid>
    <TreeView HorizontalAlignment="Left" Height="299" Margin="10,10,0,0" VerticalAlignment="Top" Width="228" ItemsSource="{Binding DataInfosView}" >
      <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
          <TextBlock DockPanel.Dock="Left" Text="{Binding InfoValue}" TextAlignment="Left" >
            <TextBlock.ContextMenu>
              <ContextMenu>
                <MenuItem Header="{Binding InfoValue}" IsEnabled="False"/>
                <MenuItem Header="Add child" Command="{Binding AddChildCmd, ElementName=window}"/>
              </ContextMenu>
            </TextBlock.ContextMenu>
          </TextBlock>
        </HierarchicalDataTemplate>
      </TreeView.ItemTemplate>
    </TreeView>
  </Grid>
</Window>

C＃：

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Data;
using System.Windows.Input;

namespace Wpf_treeView
{
    public partial class MainWindow : Window
    {
        private static readonly Random rnd = new Random();
        private List<InfoData> m_InfoData = new List<InfoData>();

        public ListCollectionView DataInfosView { get; private set; }

        public static readonly DependencyProperty AddChildProperty =
            DependencyProperty.Register("AddChildCmd", 
                                        typeof(ICommand),
                                        typeof(MainWindow));

        public ICommand AddChildCmd
        {
            get { return (ICommand) GetValue(AddChildProperty); }
            set { SetValue(AddChildProperty, value); }
        }

        public MainWindow()
        {
            AddChildCmd = new RoutedCommand();
            CommandManager.RegisterClassCommandBinding(
                GetType(), 
                new CommandBinding(AddChildCmd, AddChild));

            m_InfoData.Add(new InfoData(4));
            m_InfoData.Add(new InfoData(1));
            m_InfoData.Add(new InfoData(5));
            m_InfoData[1].Children.Add(new InfoData(3));
            m_InfoData[1].Children[0].Children.Add(new InfoData(7));

            DataInfosView = new ListCollectionView(m_InfoData);
            DataContext = this;

            InitializeComponent();
        }

        private void AddChild(object sender, RoutedEventArgs e)
        {
            ExecutedRoutedEventArgs args = (ExecutedRoutedEventArgs)e;
            InfoData info = (InfoData)args.Parameter;
            info.Children.Add(new InfoData(rnd.Next(0, 11)));
        }
    }

    class InfoData : INotifyPropertyChanged
    {
        private int infoValue;

        public int InfoValue
        {
            get { return infoValue; }
            set
            {
                if (value != infoValue)
                {
                    infoValue = value;
                    OnPropertyChanged();
                }
            }
        }

        public List<InfoData> Children { get; private set; }

        public InfoData(int infoValue)
        {
            InfoValue = infoValue;
            Children = new List<InfoData>();
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged(
            [CallerMemberName] string propertyName = null)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

推荐答案

这应该可以工作：

<TextBlock DockPanel.Dock="Left"
                           Text="{Binding InfoValue}"
                           TextAlignment="Left"
                           Tag="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}}}">
                    <TextBlock.ContextMenu>
                        <ContextMenu>
                            <MenuItem Header="{Binding InfoValue}"
                                      IsEnabled="False" />
                            <MenuItem Header="Add child"
                                      Command="{Binding Path=Parent.PlacementTarget.Tag.AddChildCmd, RelativeSource={RelativeSource Self}}" 
                                      CommandParameter="{Binding}" />
                        </ContextMenu>
                    </TextBlock.ContextMenu>
                </TextBlock>

常规的可视树中不存在ContextMenu，因此您无法向上走到达主数据上下文的树。通过使用标签，您可以将主窗口的数据上下文传递到上下文菜单中。有关与上下文菜单绑定的更多信息，请参见此答案以及此，因为它们对发生的情况提供了很好的解释

The ContextMenu doesn't exist in the regular Visual Tree, so you aren't able to walk up the tree to get to the main data context. By using the Tag you are able to "pass in" the Main Window's data context to the context menu. For some more information on binding with context menu's see this answer as well as this one as they provide some good explanations as to what is going on

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