命令绑定到ContextMenu（在ListBox中的ListBoxItem上）不工作 [英] Command bind to ContextMenu (which on ListBoxItem in ListBox) don't work

问题描述

在WPF中，使用MVVM光，有一个 Class （由一些学生组成）和 Class 持有一些学生。

右键单击学生的姓名，然后显示 MessageBox ，这样确定：

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，它不工作在这种方式（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>学生
 {
 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 
 命名空间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）; 
} 
} 
} 
} 
  
 
 
解决方案
您可以使用上下文菜单作为资源吗？
 
 
 
类似：
 < UserControl.Resources> 
 
< ContextMenu x：name =contextMenuExampleDataContext ={Binding Path = PlacementTarget，RelativeSource = {RelativeSource Self}} 
< MenuItem Header =Show Selected
 Command ={Binding Path = DataContext.RemoveStudentCommand}
 CommandParameter ={Binding Path = SelectedItem}/> 
< / ContextMenu> 
< /UserControl.Resources> 
  
然后在列表上，执行以下操作：
 < Listbox ContextMenu = {StaticResource contextMenuExample} ... /> 
  
或者你真的想使用ItemContainerStyle吗？
 
 
 
从 - > 如何右键单击列表框中的项目并打开WPF上的菜单 
 < ListBox Name =someListBoxMouseDown =someListBox_MouseDown> 
< ListBox.Resources> 
 
<！ - 定义一个上下文菜单 - > 
< ContextMenu x：Key =MyElementMenu> 
< MenuItem Header =DeleteClick =MenuItemDelete_Click/> 
< / ContextMenu> 
 
<！ - 为当前ListBox中的每个ListBoxItem设置一个上下文菜单 - > 
< Style TargetType ={x：Type ListBoxItem}> 
< Setter Property =ContextMenuValue ={StaticResource MyElementMenu}/> 
< / Style> 
 
< /ListBox.Resources> 
< ListBoxItem> ...< / ListBoxItem> 
< ListBoxItem> ...< / ListBoxItem> 
< ListBoxItem> ...< / ListBoxItem> 
< / ListBox> 
  
 
In WPF, with MVVM light, there's a Class(which is consist of some students), and the Class hold some Students.



Right-Click one Student's name, then will show a MessageBox, it is ok in this way:

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>
But, it don't work in this way (use 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>
instead of 
<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);
            }
        }
    }
}

解决方案
Can you use the contextmenu as a resource?

Something like:
<UserControl.Resources>

<ContextMenu x:name="contextMenuExample" DataContext="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Self}}">
                    <MenuItem Header="Show Selected" 
                            Command="{Binding Path=DataContext.RemoveStudentCommand}"
                            CommandParameter="{Binding Path=SelectedItem}"/>
                 </ContextMenu>
</UserControl.Resources>
Then on list, do something like:
<Listbox ContextMenu = {StaticResource contextMenuExample} ... />
Or do you really want to use ItemContainerStyle?

from -> how to right click on item from Listbox and open menu on WPF
<ListBox Name="someListBox" MouseDown="someListBox_MouseDown">
    <ListBox.Resources>

        <!--Defines a context menu-->
        <ContextMenu x:Key="MyElementMenu">
            <MenuItem Header="Delete" Click="MenuItemDelete_Click"/>
        </ContextMenu>

        <!--Sets a context menu for each ListBoxItem in the current ListBox-->
        <Style TargetType="{x:Type ListBoxItem}">
             <Setter Property="ContextMenu" Value="{StaticResource MyElementMenu}"/>
        </Style>

    </ListBox.Resources>
    <ListBoxItem>...</ListBoxItem>
    <ListBoxItem>...</ListBoxItem>
    <ListBoxItem>...</ListBoxItem>
</ListBox>


                        
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