Implementing Delegates in C#

The Zip file contains two projects. One is VB.Net and the other is C#. Each project is an example of the same use of a delegate. A base class is derived and the delegate calls a method on several classes derived from the base class. Several things are shown from this example. Using inherited base types to strinct type checking of a base type and calling class level methods from a single delegate.

Here is sample code from Delegates.cs file:

namespace DelegatesCS
{
using System;
/// <summary>
/// Author [email protected]
/// Date 02/02/2001
/// Purpose Example of Delegate usage
/// </summary>
public class Wisdom //class containing the Delegate
{
public delegate string GiveAdvice();
public string OfferAdvice(GiveAdvice Words)
{
return Words();
}
}
public class Parent //base class
{
public virtual string Advice()
{
return("Listen to reason");
}
~Parent() {}
}
public class Dad: Parent //derive from the parent
{
public Dad() {}
public override string Advice()
{
return("Listen to your Mom");
}
~Dad() {}
}
public class Mom: Parent //derive from the parent
{
public Mom() {}
public override string Advice()
{
return("Listen to your Dad");
}
~Mom() {}
}
public class Daughter //don't derive from the parent
{
public Daughter() {}
public string Advice()
{
return("I know all there is to life");
}
~Daughter() {}
}
public class Test
{
public static string CallAdvice(Parent p)//use the base type of derived class
{
Wisdom parents = new Wisdom();
Wisdom.GiveAdvice TeenageGirls = new Wisdom.GiveAdvice(p.Advice);
return(parents.OfferAdvice(TeenageGirls));
}
public static void Main()
{
Dad d = new Dad();
Mom m = new Mom();
Daughter g = new Daughter();
//these both derived from the base class
Console.WriteLine(CallAdvice(d));
Console.WriteLine(CallAdvice(m));
//cannot do this as it did not derive from the base
//Console.WriteLine(CallAdvice(g));
}
}
}