wpf - Keybinding a RelayCommand

Question

I'm using the RelayCommand in my app. It's great for putting the code in the viewmodel, but how do I bind keystrokes to my command?

RoutedUICommand has its InputGestures property, which makes the command automatically be invoked when I press the keystroke. (As an added bonus, it even makes the keystroke display in the MenuItem.) Unfortunately, there's no reusable interface for RoutedUICommand's extra properties, so I can't make a RelayUICommand that gets the same magic.

I've already tried using InputBindings:

<Window.InputBindings>
    <KeyBinding Key="PageUp" Command="{Binding SelectPreviousLayerCommand}"/>
</Window.InputBindings>

But that gets me a runtime exception, because KeyBinding.Command isn't a dependency property. (Actually, what it complains about is that KeyBinding isn't even a DependencyObject.) And since my RelayCommand is a property on my ViewModel (as opposed to the static field that RoutedUICommand is designed for), databinding is the only way I know of to reference it from XAML.

How have you guys solved this? What's the best way to bind a keystroke to a RelayCommand?

Answer 1

I don't think you can do this from XAML, for exactly the reasons you describe.

I ended up doing it in the code-behind. Although it's code, it's only a single line of code, and still rather declarative, so I can live with it. However, I'd really hope that this is solved in the next version of WPF.

Here's a sample line of code from one of my projects:

this.InputBindings.Add(new KeyBinding(
    ((MedicContext)this.DataContext).SynchronizeCommand,
    new KeyGesture(Key.F9)));

SynchronizeCommand in this case is an instance of RelayCommand, and (obviously) F9 triggers it.