Demonstrate using a static delegate without declaring an instance of the class

   


/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa

Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// StaticDl.cs -- Demonstrate using a static delegate without declaring
//                an instance of the class.
//
//                Compile this program with the following command line:
//                    C:>csc StaticDl.cs
using System;

namespace nsDelegates
{
    public class StaticDl
    {
        public delegate void StringHandler (string str);
        static public StringHandler DoString;

        static public void Main ()
        {
// Create a delegate in this class
            DoString = new StringHandler (ShowString);
            DoString ("Static delegate called");
//
// Show that the static constructor in another class is shared by instances
            clsDelegate.DoMath = new clsDelegate.MathHandler (SquareRoot);
            clsDelegate dlg1 = new clsDelegate (49);
            clsDelegate dlg2 = new clsDelegate (3.14159);
        }
// The method used with the string delegate
        static private void ShowString (string str)
        {
            Console.WriteLine (str);
        }
// The method used with the double delegate
        static private double SquareRoot (double val)
        {
            double result = Math.Sqrt (val);
            Console.WriteLine ("The square root of " + val + " is " + result);
            return (result);
        }
    }
    class clsDelegate
    {
        public delegate double MathHandler (double val);
        static public MathHandler DoMath;
// The constructor invokes the delegate if it is not null.
        public clsDelegate (double val)
        {
            value = val;
            if (DoMath != null)
                sqrt = DoMath (value);
        }
        double value;
        double sqrt = 0;
    }
}