Last Updated: February 25, 2016
· to_pe

Generic EventArgs class

Sometimes you want a simple event handler in C# that will pass single value e.g. a string. The default EventHandler<T> type expects that the generic T type inherits EventArgs which requires that we create a new class that inherits EventArgs. For passing a simple string or a number, this is simply too much boilerplate code.

But we can create a generic EventArgs class, something that is missing in FCL and which will wrap our variable thus satisfying EventHandler<T>.

public class EventArgs<T> : EventArgs
    public T Value { get; private set; }

    public EventArgs(T val)
        Value = val;

You declare your event with the following syntax:

public event EventHandler<EventArgs<string>> StringReceivedEvent;

The following snippet demonstrates how to use it:

public void OnStringReceived()
    if (StringReceivedEvent != null)
        StringReceivedEvent(this, new EventArgs<string>(somestring));

// client code
StringReceivedEvent += (o, e) => Console.WriteLine(e.Value);