How do you bind a command to a MenuItem (WPF)?

Question

Here is my code from the View.xaml.cs:

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:

<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.

Persnickety

Did you set the DataContext? – Wrennie

I found the solution to my problem. I was using a ViewModel that had a property in it that was another ViewModel type and I needed to scope down to that propery by doing this: Command="{Binding ActiveVM.CloseCommand}" – Persnickety

I have found a solution to your question [#899352 [1]: #899352 – Splenectomy

Answer 1

ContextMenu is not part of the VisualTree, that's why the DataContext will not be inherited. Here ContextMenu.PlacementTarget is some kind of relay to get the Window:

<MenuItem Name="menuItem_Close" Header="Close"
          Command="{Binding Path=PlacementTarget.DataContext.CloseCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}" />

Hubie

Are you sure it doesn't get the DataContext? In my test it seems to be inheriting the DataContext as you would expect ... – Gudgeon

I tried your code for the Command="..." but it did not work - just as before - nothing happed. – Persnickety

@dbaseman According to this Popup creates its own visualtree. This means no DataContext inheritance for ContextMenu which is placed in a Popup. – Hubie

@JacksonDeanGoodwin Any binding errors? Are you sure that DataContext is set for Window? Maybe try a Button with your Command binding in Window directly for that. – Hubie

Thanks for this. How should I bind a static ICommand to a MenuItem not using a ViewModel binding? I am currently using (which is not working) Command="{x:Static ...}" but that doesn't seem to work with the solution you have provided here. Please help. – Whitsuntide

Answer 2

Old question, new answer. For me the problem was that GalaSoft.MvvmLight.Command.RelayCommand didn'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.

Petrarch

Answer 3

for binding cross visual tree, refer to

Binding Visibility for DataGridColumn in WPF

or jsut try search BindingProxy

Valli