如何将命令绑定到动态上下文菜单

Question

我正在使用 c#、prism、wpf。我想在一个listview中动态创建一个上下文列表，如下图：

当我单击这些菜单项时，它将回调我的自定义函数。在该函数中，我可以识别单击了哪个菜单项，例如，我可以获取菜单项的标题。

我尝试添加命令标记并绑定到 ICommand。但是点击后没有任何反应。

我从网上阅读了不同的示例，但它们从未同时显示 xaml 和 viewmodel 的实现。我想问一下怎么办？非常感谢。

在 App.xaml.cs 中：

ViewModelLocationProvider.Register<MainWindowView, MainWindowViewModel>();

以下是我的 xaml：

<ListView Grid.Row="2"  ItemsSource="{Binding ServiceObjects}" ItemContainerStyle="{StaticResource LstBoxItemStyleNormal}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid>
                <TextBlock Text="{Binding ServiceName}">
                    <TextBlock.ContextMenu>
                        <ContextMenu ItemsSource="{Binding ContextMenuList}">
                            <ContextMenu.ItemTemplate>
                                <HierarchicalDataTemplate>
                                    <MenuItem Header="{Binding MenuName}" Command="{Binding ConfirmButtonCommand}"/>
                                </HierarchicalDataTemplate>
                            </ContextMenu.ItemTemplate>
                        </ContextMenu>
                    </TextBlock.ContextMenu>
                </TextBlock>
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

以下是我的视图模型：

class MainWindowViewModel : BindableBase
{
    public class MenuNode : BindableBase
    {
        private string _menuName;
        public string MenuName
        {
            get => _menuName;
            set => SetProperty(ref _menuName, value);
        }
    }
    public class ServiceNode : BindableBase
    {
        private string _serviceName;
        public string ServiceName
        {
            get => _serviceName;
            set => SetProperty(ref _serviceName, value);
        }
        public ObservableCollection<MenuNode> ContextMenuList { get; } = new ObservableCollection<MenuNode>();
    }
    public ObservableCollection<ServiceNode> ServiceObjects { get; } = new ObservableCollection<ServiceNode>();
    
    public MainWindowViewModel()
    {
        for (int i = 0; i < 10; i++)
        {
            ServiceNode tempNode = new ServiceNode { ServiceName = "AP", State = "Normal" };
            tempNode.ContextMenuList.Add(new MenuNode { MenuName = "A Item" });
            tempNode.ContextMenuList.Add(new MenuNode { MenuName = "B Item" });
            tempNode.ContextMenuList.Add(new MenuNode { MenuName = "C Item" });
            ServiceObjects.Add(tempNode);
        }
        ConfirmButtonCommand = new DelegateCommand(HandleConfirmButtonCommand);
    }
    public ICommand ConfirmButtonCommand { get; }

    private void HandleConfirmButtonCommand()
    {
        
    }

Answer 1

首先绑定到Command 的MenuItem 应该是大括号：{Binding ConfirmButtonCommand}。
其次，你的命令是在MainWindowViewModel类中定义的，而DataContext对于MenuItem是MenuNode，所以找不到命令。
最简单的解决方法是 - 为 List 命名，并在绑定到命令时，参考其 DataContext。
例如：

<ListView x:Name="list" ...>

然后

<MenuItem Header="{Binding MenuName}" Command="{Binding DataContext.ConfirmButtonCommand, ElementName=list}"/>

另外，对于命令，您可能还需要知道单击了什么ServiceNode，您可以通过CommandParameter 传递它（从ContextMenu 获取DataContext，其中包含MenuItem）：

<MenuItem ... CommandParameter="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType=ContextMenu}}">

Answer 2

这是我最后使用的答案。谢谢

在 App.xaml.cs 中：

ViewModelLocationProvider.Register<MainWindowView, MainWindowViewModel>();

以下是我的 xaml：

<ListView Grid.Row="2"  ItemsSource="{Binding ServiceObjects}" ItemContainerStyle="{StaticResource LstBoxItemStyleNormal}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid>
                <TextBlock Text="{Binding ServiceName}" Tag="{Binding DataContext, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ListView}}">
                    <TextBlock.ContextMenu>
                        <ContextMenu ItemsSource="{Binding ContextMenuList}">
                            <ContextMenu.ItemTemplate>
                                <HierarchicalDataTemplate>
                                    <MenuItem Header="{Binding MenuName}"
                                              Command="{Binding PlacementTarget.Tag.ConfirmButtonCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ContextMenu}}"
                                              CommandParameter="Binding MenuName"/>
                                </HierarchicalDataTemplate>
                            </ContextMenu.ItemTemplate>
                        </ContextMenu>
                    </TextBlock.ContextMenu>
                </TextBlock>
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

以下是我的视图模型：

class MainWindowViewModel : BindableBase
{
    public class MenuNode : BindableBase
    {
        private string _menuName;
        public string MenuName
        {
            get => _menuName;
            set => SetProperty(ref _menuName, value);
        }
    }
    public class ServiceNode : BindableBase
    {
        private string _serviceName;
        public string ServiceName
        {
            get => _serviceName;
            set => SetProperty(ref _serviceName, value);
        }
        public ObservableCollection<MenuNode> ContextMenuList { get; } = new ObservableCollection<MenuNode>();
    }
    public ObservableCollection<ServiceNode> ServiceObjects { get; } = new ObservableCollection<ServiceNode>();
    
    public MainWindowViewModel()
    {
        for (int i = 0; i < 10; i++)
        {
            ServiceNode tempNode = new ServiceNode { ServiceName = "AP", State = "Normal" };
            tempNode.ContextMenuList.Add(new MenuNode { MenuName = "A Item" });
            tempNode.ContextMenuList.Add(new MenuNode { MenuName = "B Item" });
            tempNode.ContextMenuList.Add(new MenuNode { MenuName = "C Item" });
            ServiceObjects.Add(tempNode);
        }
        ConfirmButtonCommand = new DelegateCommand<string>(HandleConfirmButtonCommand);
    }
    public ICommand ConfirmButtonCommand { get; }

    private void HandleConfirmButtonCommand(string parameter)
    {
        
    }