wpf 命令绑定到 ContextMenu（在 ListBox 中的 ListBoxItem 上）不起作用
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Command bind to ContextMenu (which on ListBoxItem in ListBox) don't work
提问by SubmarineX
In WPF, with MVVM light, there's a Class(which is consist of some students), and the Classhold some Students.
在 WPF 中，使用 MVVM 灯，有一个Class（由一些学生组成）和Class一些Students。
Right-Click one Student's name, then will show a MessageBox, it is ok in this way:
右击一个学生的名字，会显示一个MessageBox，这样就可以了：
ClassDetailView.xaml
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):
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>
instead of
代替
<ListBox.ContextMenu>
<ContextMenu ...>
...
<ContextMenu />
</ListBox.ContextMenu>
ClassDetailViewModel.cs
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
学生视图模型.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);
}
}
}
}
回答by James
You need a proxy to bind commands to a context menu of a listboxitem. See the answer here:
您需要一个代理来将命令绑定到列表框项的上下文菜单。请看这里的答案：
回答by sexta13
Can you use the contextmenu as a resource?
您可以将上下文菜单用作资源吗？
Something like:
就像是：
<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:
然后在列表中，执行以下操作：
<Listbox ContextMenu = {StaticResource contextMenuExample} ... />
Or do you really want to use ItemContainerStyle?
或者你真的想使用 ItemContainerStyle 吗？
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>
回答by Mark Green
By moving the ContextMenu to the ListBoxItem, you've changed the DataContext from ClassDetailsViewModel(the DataContext of the ListBox) to StudentViewModel (the DataContext of the ListBoxItem). As a result, you need to change your path to access the parent ListBox's DataContext to get access to the RelayCommand.
通过将 ContextMenu 移动到 ListBoxItem，您已将 DataContext 从 ClassDetailsViewModel（ListBox 的 DataContext）更改为 StudentViewModel（ListBoxItem 的 DataContext）。因此，您需要更改访问父 ListBox 的 DataContext 的路径才能访问 RelayCommand。
<ListBox.ItemContainerStyle>
<Style TargetType="ListBoxItem">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBox}}, Path=DataContext}">
<MenuItem Header="Show Selected"
Command="{Binding Path=RemoveStudentCommand}"
CommandParameter="{Binding Path=SelectedItem}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</ListBox.ItemContainerStyle>
