/*
 * C# Program to IIlustrate Handling an Event Declared in an Interface
 */
namespace interfaceevents
{
    using System;
 
    public interface square
    { 
        event EventHandler Draw;
    }
    public interface rectangle
    {
        event EventHandler Draw;
    } 
    public class Shape : square, rectangle
    { 
        event EventHandler DrawEvent1;
        event EventHandler DrawEvent2;
        object objectLock = new Object();
        event EventHandler square.Draw
        {
            add
            {
                lock (objectLock)
                {
                    DrawEvent1 += value;
                }
            }
            remove
            {
                lock (objectLock)
                {
                    DrawEvent1 -= value;
                }
            }
        } 
        event EventHandler rectangle.Draw
        {
            add
            {
                DrawEvent2 += value;
            }
             remove
             {
                 DrawEvent2 -= value;
 
            }
 
        }
        public void Draw()
        {
            EventHandler handler = DrawEvent1;
            if (handler != null)
            {
                handler(this, new EventArgs());
            }
            Console.WriteLine("Drawing a shape.");
            handler = DrawEvent2;
            if (handler != null)
            {
                handler(this, new EventArgs());
            }
        }
    }
    public class classA
    {
        // References the shape object as an square 
        public classA(Shape shape)
        {
            square d = (square)shape;
            d.Draw += new EventHandler(d_Draw);
        }
 
        void d_Draw(object sender, EventArgs e)
        {
            Console.WriteLine("ClassA receives the square event.");
        }
    } 
    public class classB
    {
        public classB(Shape shape)
        {
            rectangle d = (rectangle)shape;
            d.Draw += new EventHandler(d_Draw);
        }
 
        void d_Draw(object sender, EventArgs e)
        {
            Console.WriteLine("ClassB receives the rectangle event.");
        }
    }
 
    public class Program
    {
        static void Main(string[] args)
        {
            Shape shape = new Shape();
            classA sub = new classA(shape);
            classB sub2 = new classB(shape);
            shape.Draw();
            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();
        }
    }
}