Question

I am getting ready to create a generic EventArgs class for event args that carry a single argument:

public class EventArg<T> : EventArgs
{
    // Property variable
    private readonly T p_EventData;

    // Constructor
    public EventArg(T data)
    {
        p_EventData = data;
    }

    // Property for EventArgs argument
    public T Data
    {
        get { return p_EventData; }
    }
}

Before I do that, does C# have the same feature built in to the language? I seem to recall coming across something like that when C# 2.0 came out, but now I can’t find it.

Or to put it another way, do I have to create my own generic EventArgs class, or does C# provide one? Thanks for your help.

Answer 1

No. You probably were thinking of EventHandler<T>, which allows you to define the delegate for any specific type of EventArgs.

I personally don’t feel that EventArgs<T> is quite as good of a fit, though. The information used as a "payload" in the event args should be, in my opinion, a custom class to make its usage and expected properties very clear. Using a generic class will prevent you from being able to put meaningful names into place. (What does "Data" represent?)