WPF DataBinding, MVVM and Routed Events - wpf

Question

When I try to call my UserControl's custom RoutedEvent in my XAML using a Command Delegate binding I get this exception:
Exception thrown: 'System.Windows.Markup.XamlParseException' in PresentationFramework.dll
Additional information: 'Provide value on 'System.Windows.Data.Binding' threw an exception.'
My WPF application is using MVVM and IOC so all the logic is in the view models.
The DataContext for a view is set in a resource dictionary:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vw="clr-namespace:MyApp.Order.View"
xmlns:vm="clr-namespace:MyApp.Order.ViewModel">
<DataTemplate DataType="{x:Type vm:OrderViewModel}">
<vw:OrderView />
</DataTemplate>
etc
I have a UserControl in another project within this solution that happens to be a Keyboard and I've wired up a routed event like so:
public partial class MainKeyboard : UserControl
{
public static DependencyProperty TextProperty;
public static DependencyProperty FirstLetterToUpperProperty;
// Create a custom routed event by first registering a RoutedEventID
// This event uses the bubbling routing strategy
public static readonly RoutedEvent TapEvent = EventManager.RegisterRoutedEvent(
"Tap", RoutingStrategy.Bubble,
typeof(RoutedEventHandler),
typeof(MainKeyboard));
// Provide CLR accessors for the event
public event RoutedEventHandler Tap
{
add { AddHandler(TapEvent, value); }
remove { RemoveHandler(TapEvent, value); }
}
// This method raises the Tap event
void RaiseTapEvent()
{
RoutedEventArgs newEventArgs = new RoutedEventArgs(MainKeyboard.TapEvent);
RaiseEvent(newEventArgs);
}
Now, when I consume this event using my XAML declration and bind the Command to the view model's command delegate like I normally do:
<assets:MainKeyboard Tap="{Binding DoTapCommandInViewModel}" />
I get an error, but I can do this everywhere else, like in a button right above this code:
<Button Content="GetStarted"
Command="{Binding DoTapCommandInViewModel}"
Style="{StaticResource GetStartedButton}" />
What does work for me is calling a method in the code behind of this XAML file:
<assets:MainKeyboard Tap="MainKeyboard_OnTap"/>
The datacontext for both the button and the keyboard user control are the same; they live in the same view.
So why can't I bind this event directly to a command?

Answer 1

Dytori was right; I needed an Event Trigger on the control declaration. Ah Wpf...
<assets:MainKeyboard>
<b:Interaction.Triggers>
<b:EventTrigger EventName="Tap">
<b:InvokeCommandAction Command="{Binding DoTapTapTap}"/>
</b:EventTrigger>
</b:Interaction.Triggers>
</assets:MainKeyboard>