wpf - 命令绑定(bind)到 ContextMenu(在 ListBox 中的 ListBoxItem 上)不起作用

Question

这个问题已经有答案了:

ContextMenu Command Binding to parent and to self (1 个回答)

已关闭 7 年前。

在 WPF 中，通过 MVVM 轻量级，有一个 Class (由一些学生组成)，以及 Class持有一些Student s。

右键单击一个学生的名字，然后会显示MessageBox ，这样就可以了:

ClassDetailView.xaml

<UserControl DataContext="{Binding ClassDetail, Source={StaticResource Locator}}">
    <DockPanel>
        <ListBox 
            ItemsSource="{Binding Students}" 
            DisplayMemberPath="Name">
            <ListBox.ContextMenu>
                <ContextMenu DataContext="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Self}}">
                    <MenuItem 
                        Header="Show Selected" 
                        Command="{Binding Path=DataContext.RemoveStudentCommand}"
                        CommandParameter="{Binding Path=SelectedItem}"/>
                </ContextMenu>
            </ListBox.ContextMenu>
        </ListBox>
    </DockPanel>
</UserControl>

但是，它不能以这种方式工作(使用 ListBox.ItemContainerStyle):

<ListBox.ItemContainerStyle>
    <Style TargetType="ListBoxItem">
        <Setter Property="ContextMenu">
            <Setter.Value>
                <ContextMenu DataContext="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Self}}">
                    <MenuItem Header="Show Selected" 
                            Command="{Binding Path=DataContext.RemoveStudentCommand}"
                            CommandParameter="{Binding Path=SelectedItem}"/>
                 </ContextMenu>
             </Setter.Value>
         </Setter>
     </Style>
 </ListBox.ItemContainerStyle>

而不是

<ListBox.ContextMenu>
    <ContextMenu ...>
        ...
    <ContextMenu />
</ListBox.ContextMenu>

ClassDetailViewModel.cs

namespace ContextMenu.ViewModel
{
    public class ClassDetailViewModel : ViewModelBase
    {
        public ClassDetailViewModel()
        {
            CreateData();
        }

        public void CreateData()
        {
            students.Add(new StudentViewModel() { Name = "QQ" });
            students.Add(new StudentViewModel() { Name = "WW" });
            students.Add(new StudentViewModel() { Name = "EE" });
            students.Add(new StudentViewModel() { Name = "RR" });
            students.Add(new StudentViewModel() { Name = "AA" });
            students.Add(new StudentViewModel() { Name = "SS" });
            students.Add(new StudentViewModel() { Name = "DD" });
            students.Add(new StudentViewModel() { Name = "FF" });
            students.Add(new StudentViewModel() { Name = "ZZ" });
            students.Add(new StudentViewModel() { Name = "XX" });
        }

        public const string StudentsPropertyName = "Students";
        private ObservableCollection<StudentViewModel> students = 
            new ObservableCollection<StudentViewModel>();
        public ObservableCollection<StudentViewModel> Students
        {
            get { return students; }
            set
            {
                if (students == value) { return; }
                students = value;
                RaisePropertyChanged(StudentsPropertyName);
            }
        }

        private RelayCommand<StudentViewModel> removeStudentCommand;
        public RelayCommand<StudentViewModel> RemoveStudentCommand
        {
            get
            {
                return removeStudentCommand
                    ?? (removeStudentCommand =
                        new RelayCommand<StudentViewModel>(ExecuteRemoveStudentCommand));
            }
        }
        private void ExecuteRemoveStudentCommand(StudentViewModel student)
        {
            if (null == student) { return; }
            MessageBox.Show(string.Format("RemoveStudent:{0}", student.Name));
        }
    }
}

StudentViewModel.cs

namespace ContextMenu.ViewModel
{
    public class StudentViewModel : ViewModelBase
    {
        public const string NamePropertyName = "Name";
        private string name = "";
        public string Name
        {
            get { return name; }
            set
            {
                if (name == value) { return; }
                name = value;
                RaisePropertyChanged(NamePropertyName);
            }
        }
    }
}

Answer 1

您需要一个代理将命令绑定(bind)到列表框项目的上下文菜单。请参阅此处的答案:

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