如何将命令绑定到 MenuItem (WPF)？
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How do you bind a command to a MenuItem (WPF)?
提问by Hymanson Dean Goodwin
Here is my code from the View.xaml.cs:
这是我来自 View.xaml.cs 的代码：
private RelayCommand _closeCommand;
public ICommand CloseCommand
{
get
{
if (_closeCommand == null)
{
_closeCommand = new RelayCommand(param => this.OnClose());
}
return _closeCommand;
}
}
public void OnClose()
{
Close();
}
And here is some code from my View.xaml:
这是我的 View.xaml 中的一些代码：
<Window.ContextMenu>
<ContextMenu>
<MenuItem Name="menuItem_Close" Header="Close" Command="{Binding CloseCommand}" />
</ContextMenu>
</Window.ContextMenu>
When I run the program and select the close menu item, nothing happens. The CloseCommand code doesn't even get executed.
当我运行程序并选择关闭菜单项时，没有任何反应。CloseCommand 代码甚至不会被执行。
回答by LPL
ContextMenuis not part of the VisualTree, that's why the DataContextwill not be inherited. Here ContextMenu.PlacementTargetis some kind of relay to get the Window:
ContextMenu不是 VisualTree 的一部分，这就是为什么它DataContext不会被继承。这ContextMenu.PlacementTarget是某种继电器来获得Window：
<MenuItem Name="menuItem_Close" Header="Close"
Command="{Binding Path=PlacementTarget.DataContext.CloseCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}" />
回答by SnakE
Old question, new answer. For me the problem was that GalaSoft.MvvmLight.Command.RelayCommanddidn't support closures for the action. RelayCommand stores a weak reference to the action so a closure gets deallocated almost immediately. The action must be a model method or be retained in some other way.
老问题，新答案。对我来说，问题是GalaSoft.MvvmLight.Command.RelayCommand不支持关闭操作。RelayCommand 存储对动作的弱引用，因此闭包几乎立即被释放。操作必须是模型方法或以其他方式保留。
回答by user2024396
for binding cross visual tree, refer to
绑定交叉可视化树，参考
Binding Visibility for DataGridColumn in WPF
or jsut try search BindingProxy
或 jsut 尝试搜索 BindingProxy
