Here is the code which defines a C# EventHandler, as written in the documentation, it represents the method that will handle an event that has no event data:

// Summary:
//     Represents the method that will handle an event that has no event data.
//
// Parameters:
//   sender:
//     The source of the event.
//
//   e:
//     An System.EventArgs that contains no event data.
[Serializable]
[ComVisible(true)]
public delegate void EventHandler(object sender, EventArgs e);

So after declaring a specific event:

private event EventHandler OnSomethingHappened;

We need to write a method to raise this event:

Did you ever need to convert List(T1) to List(T2)? One example might be when implementing an interface. you might need to expose a collection of other interfaces (or maybe the same interface), But you usually hold the concrete type implementing the interface in the collection. Lets look at the following example: