不带标签的 DataTemplate 中 MenuItem 的绑定命令
我想将 ViewModel 中的命令绑定到 DataTemplate 中的 menuItem。我可以使用标签来做到这一点。有没有任何方法可以完成相同的任务但不使用标签。
<Window.Resources>
<DataTemplate x:Key="StudentListBoxItemTemplate">
<StackPanel Tag="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBox}}}">
<TextBlock Text="{Binding Name}"/>
<StackPanel.ContextMenu>
<ContextMenu>
<MenuItem Header="Trigger" Command="{Binding PlacementTarget.Tag.TriggerCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}"/>
</ContextMenu>
</StackPanel.ContextMenu>
</StackPanel>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ListBox
ItemsSource="{Binding StudentList}"
ItemTemplate="{StaticResource StudentListBoxItemTemplate}">
</ListBox>
</StackPanel>
我的视图模型
public class MainViewModel {
public ICommand TriggerCommand { ... }
public ObservableList<Student> StudentList { ... }
}
I want to bind a command in my ViewModel to a menuItem which is in DataTemplate. I can do that with using Tag. Is there any method which can do the same task but without using tag.
<Window.Resources>
<DataTemplate x:Key="StudentListBoxItemTemplate">
<StackPanel Tag="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBox}}}">
<TextBlock Text="{Binding Name}"/>
<StackPanel.ContextMenu>
<ContextMenu>
<MenuItem Header="Trigger" Command="{Binding PlacementTarget.Tag.TriggerCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}"/>
</ContextMenu>
</StackPanel.ContextMenu>
</StackPanel>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ListBox
ItemsSource="{Binding StudentList}"
ItemTemplate="{StaticResource StudentListBoxItemTemplate}">
</ListBox>
</StackPanel>
My ViewModel
public class MainViewModel {
public ICommand TriggerCommand { ... }
public ObservableList<Student> StudentList { ... }
}
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根据您当前的设计，您需要从
ContextMenu通过StackPanel并返回到包含ListBox的DataContext代码>.造成这种尴尬的原因是StackPanel的DataContext已经缩小到特定的学生。至少有两种方法可以让这变得更容易：
Student中提供TriggerCommand属性，以便该命令就在您需要的地方ParentStudent中的 > 属性来逃避缩小的范围With your current design, you need to get from the
ContextMenuthrough theStackPaneland back to theDataContextof the containingListBox. What makes this awkward is that theDataContextof theStackPanelis already narrowed down to a particular student.There are at least two ways to make this easier:
TriggerCommandproperty inStudentso the command is right there where you need itParentproperty in theStudentto escape the narrowed scope您可以尝试将点击事件添加到menuItem，如下
尝试将命令绑定到Click。我的 VS 已关闭，因此目前无法检查。
You can try to add click event to the menuItem like following
Try binding the command to Click. My VS is down so can't check at this moment.
一种方法是获取视图模型中定义的上下文菜单集合演示，其中将包含标题字符串和命令操作（可能带有谓词）。
视图模型创建上下文菜单项的可观察集合，视图将其绑定到上下文菜单项源并将显示成员路径设置为标题字符串。
One way would be to get the context menu collection presentation defined in your viewmodel, which will contain the header string and command action (maybe with predicate).
The viewmodel creates an observable collection of the contextmenu items and the view binds that to ContextMenu itemssource and sets the displaymember path to header string.