'event': event in interface cannot have get or set accessors
You cannot define the get or set accessor functions of an event in an interface.
The following sample generates CS0069:
using System; public delegate void EventHandler(object sender, int e); public interface a { event EventHandler Click { // CS0069 get { return null; } set { } } } // try the following line instead // event EventHandler Click; public class b { public static void Main() { } }