Delegates and events in the frontend?

You can specify an event in an interface, but you cannot declare a delegate (or any other type) - at least not in C #. For instance:

// Valid
public delegate void BarHandler(object sender, EventArgs e);        
public interface IFoo
{
    event BarHandler Bar;
}

// Invalid
public interface IFoo
{
    delegate void BarHandler(object sender, EventArgs e);        
    event BarHandler Bar;
}