If you look at my KeyBehavior you notice that it is doing two things: register for events so that the behavior can be triggered and handle the actual command invocation. In order to enhance reuse we can refactor this KeyBehavior in a KeyTrigger and an InvokeCommandAction. Well, we’re not going to do that, because they exist already in the silverlight sdk.

A shortcoming of the InvokeCommandAction is that it can only invoke commands on the FrameworkElement itself, thus we write a custom implementation that finds commands on the DataContext instead

public class InvokeCommandAction : TriggerAction<frameworkElement>
{
public string CommandName { get; set; }

protected override void Invoke(object parameter)
{
var viewModel = AssociatedObject.DataContext;
GetCommandAndExecuteIt(viewModel, CommandName);
}

void GetCommandAndExecuteIt(object viewModel, string commandName)
{
var command = viewModel.GetPropertyValue<icommand>(commandName);
if(command.CanExecute(null)) command.Execute(null);
}
}


And now we can drag this action on our design surface in Blend and select a trigger that goes with it

All we have to do is choose the Key and Command to invoke

In XAML this looks like

<interactivity:Interaction.Triggers>
<ii:KeyTrigger Key="Right">
<inf:InvokeCommandAction CommandName="PlayerRight"/>
</ii:KeyTrigger>
<ii:KeyTrigger Key="Left">
<inf:InvokeCommandAction CommandName="PlayerLeft"/>
</ii:KeyTrigger>
<ii:KeyTrigger Key="Up">
<inf:InvokeCommandAction CommandName="PlayerUp"/>
</ii:KeyTrigger>
<ii:KeyTrigger Key="Down">
<inf:InvokeCommandAction CommandName="PlayerDown"/>
</ii:KeyTrigger>
</interactivity:Interaction.Triggers>


I guess this ends our exploration of the behavior features in Silverlight.