C#: Where should you place event handler delegates?

Question

I have this class:

public class GenericEventArgs<T> : EventArgs
{
    public GenericEventArgs() : this(default(T)) {}
    public GenericEventArgs(T value) { Value = value; }
    public T Value { get; private set; }
}

And this event handler delegate for it:

public delegate void GenericEventHandler<T>(object sender, GenericEventArgs<T> e);

I currently have these in the same file together in a namespace. Is that considered bad/messy/etc.? Cause, in general I would say that each file should contain only one class. So to have it clean I would prefer to have the GenericEventArgs class in the file alone. But then I have this GenericEventHandler<T> delegate that I am not sure where I should place. Should it have its own file? With just... that one line kind of? (and the namespace of course)

How do you usually do this?

Answer 1

Well I'd put the GenericEventArgs<T> class in it's own file called

GenericEventArgs_T.cs in the same namespace as everything else.

And I'd put your delegate (and event if there is one) in the class that's going to have that event exposed on it.

Answer 2

When I wanted to create my own eventhandler delegates, I used to create one file which had the name of the EventArgs class that I used in my own eventhandler delegate. For instance 'MyEventArgs.cs'.

That file contained the MyEventArgs class, and the MyEventHandler delegate that used this class.

Now however, I use the existing generic EventHandler (EventHandler<T>), and I only have to create my custom EventArgs class. So, this 'problem' doesn't exists anymore for me. :)

Answer 3

Any reason for not using EventHandler<TEventArgs>? I thought there was an equivalent EventArgs<T> but I can't see it at the moment... Anyway, I'd put GenericEventArgs in GenericEventArgs.cs

Personally, when I want to introduce my own delegate types (which is increasingly rare, to be honest) I create a Delegates.cs file with all the appropriate delegates for the namespace in. Then I know where to find them without having a file for a single declaration.

Answer 4

I'd do what you are already doing and then put all delegates that are not used for events in a separate .cs file called Delegates.cs or something similar.