Custom RoutedEvent as EventTrigger

I have my own form class

public sealed class MirrorTile : Shape

and in this class I added an event

public static readonly RoutedEvent SelectedEnterEvent = EventManager.RegisterRoutedEvent("SelectedEnter", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(MirrorTile));

public event RoutedEventHandler SelectedEnter
{
    add
    {
        this.AddHandler(SelectedEnterEvent, value);
    }

    remove
    {
        this.RemoveHandler(SelectedEnterEvent, value);
    }
}

and want to use it that way

<shapes:MirrorTile>
    <shapes:MirrorTile.Triggers>
        <EventTrigger RoutedEvent="SelectedEnter">
            <BeginStoryboard Storyboard="{StaticResource SelectShape}"/>
        </EventTrigger>
    </shapes:MirrorTile.Triggers>
</shapes:MirrorTile>

After the startup, I get an exception: {"RoutedEventConverter cannot convert from System.String."}

What am I doing wrong and how can I fix this problem?