Hotkey commands for Silverlight in MVVM?

Question

I'm trying to fire commands based on keystrokes in Silverlight. As I understand you cannot use AccessKey or AcceleratorKey in Silverlight. Also it looks like the might be helpful attached property InputBindings does not work either.

I started looking in other places. It looked like Prism was the way to get commands working in Silverlight, so I checked that out. However they only have a Click handler, which isn't even a useful starting point for getting key commands set up.

Am I just missing some part of Prism? Or is there a good standard way of handling hotkeys with MVVM Silverlight?

Answer 1

Do you mean like Ctrl+v or such I have seen the following example at the MSDN site.

void Canvas_KeyUp(object sender, KeyEventArgs e)
{
    //check for the specific 'v' key, then check modifiers
    if (e.Key==Key.V) { 
        if ((Keyboard.Modifiers & ModifierKeys.Control) == ModifierKeys.Control) {
        //specific Ctrl+V action here
        }
    } // else ignore the keystroke
}

Answer 2

The MVVM toolkit contains an interesting CommandReference class that allows you to bind InputBindings to ViewModel commands. I'm not sure it works for Silverlight, but you can give it a try...

OK, as RandomEngy pointed out, there are no InputBindings in Silverlight...

However, I think you could use attached behaviors. It's a way to "bind" an event to a command of the ViewModel. Marlon Grech has a good implementation here

Answer 3

It sounds like you're looking for a "codeless" MVVMish way of handling the KeyUp/KeyPress/KeyDown event.

Option #1: Prism.
You've mentioned it only ships with the Click command. However, you can add your own attached DPs to enable commands for whatever event you'd like (like KeyUp/KeyDown/KeyPress).

If you're looking for a sample on that Corey has a good one for ToggleButton.Checked/Unchecked events.
http://www.85turns.com/2009/06/24/togglebutton-command-for-prism/

<ToggleButton x:Name="ToggleButton1" 
   customCommands:Checked.Command="{Binding CheckedCommand}"
   customCommands:UnChecked.Command="{Binding UnCheckedCommand}"
        Margin="8,8,0,8" Content="Check me"
        />

Also, Erik Mork has an excellent video that gives you a good overview on commands and how to create a custom command Attached DP. http://development-guides.silverbaylabs.org/Video/Prism-Commands

Option #2: Blend Triggers
The Expression Blend SDK ships with Triggers and Behaviours that are spot on to what you're try to do.
Blend Examples codeplex project ships with a EventTrigger you could use:

<i:EventTrigger EventName="Click">
      <si:InvokeDataCommand Command="{Binding ShoppingCart.CheckOutCommand}"/>
</i:EventTrigger>

Or, you could create your own custom Trigger for Key stroke events and do there whatever you'd like. Here's a sample:
http://azurecoding.net/blogs/brownie/archive/2009/04/06/blend-behaviors-ftw.aspx