Routed Events in WPF - using an Action delegate

Question

Hi, I'm developing a user control, and wish to use a routed event. I notice that there are two delegates provided - RoutedEventHandler, and RoutedPropertyChangedEventHandler. The first that doesn't pass along any information, and the second that takes the old and new values of a property change. However, I need to pass just a single piece of information, so I want the equivalent of an Action delegate. Is there anything provided? Can I use an Action delegate?

Answer 1

Create a subclass of RoutedEventArgs to hold your additional data, and use EventHandler<T> with your args class. This will be convertible to RoutedEventHandler and the additional data will be available in your handlers.

You could create a generic RoutedEventArgs class that holds a single parameter of any type, but creating a new class usually makes the code easier to read and easier to modify to include more parameters in the future.

public class FooEventArgs
    : RoutedEventArgs
{
    // Declare additional data to pass here
    public string Data { get; set; }
}

public class FooControl
    : UserControl
{
    public static readonly RoutedEvent FooEvent =
        EventManager.RegisterRoutedEvent("Foo", RoutingStrategy.Bubble, 
            typeof(EventHandler<FooEventArgs>), typeof(FooControl));

    public event EventHandler<FooEventArgs> Foo
    {
        add { AddHandler(FooEvent, value); }
        remove { RemoveHandler(FooEvent, value); }
    }

    protected void OnFoo()
    {
        base.RaiseEvent(new FooEventArgs()
        {
            RoutedEvent = FooEvent,
            // Supply the data here
            Data = "data",
        });
    }
}