using System;

​

public class MyMain

{

     public static void Main()

     {

         Teacher jussi = new Teacher();

                                    // instantiate inner class object

         jussi.RegisterWithListener(new Teacher.TeacherHandler(OnTeachEvent));

         jussi.teacherIsBoring = false;

         jussi.teach();

     }

    // Since teacher is not boring and we are listening,

    // this method is called

    public static void OnTeachEvent(string m)

    {

         Console.WriteLine("Important message from teacher!");

         Console.WriteLine(m);

     }

}

​

internal class Teacher {

    // A new inner class is created here! The class inherits System.MulticastDelegate

    // This can point to whatever class that is void and one string argument. This could be also outer-class.

    public delegate void TeacherHandler(string msg);

​

    // Declare an attribute type of the new class.

    private TeacherHandler listOfHandlers;

​

    // Helper method for assigning the attribute

    public void RegisterWithListener(TeacherHandler methodToCall) {

        listOfHandlers = methodToCall;

    }

​

    public bool teacherIsBoring { get; set; }

​

    public void teach() {

        // If teacher is not boring

        if (!teacherIsBoring)

        {

            // And there are someone listening

            if (listOfHandlers != null)

            {

                // Send message to the listener.

                listOfHandlers("C# is cool!");

            }

        }

    }

}