Delegate Covariance and Contravariance C#

Covariance: (Return type of Method is more specific than that of the delegate)

A method targeted by the delegate can return a derived type, of the type expected by the delegate. For example the delegate expects an animal back and it gets back a dog. This is called covariance.

using System;

namespace ContravarianceExample

{

    class Program

    {

        public delegate Animal ADelegate();

        static void Main(string[] args)

        {

            ADelegate del = GiveDog;

            var  animal= del();

            Console.WriteLine(animal.GetType());//Dog

        }

        static Dog  GiveDog()

        {

            return new Dog();

        }

    }

    public class Animal

    {

    }

    public class Dog : Animal

    {

    }

}

Contravariance:(Input paramater of delegate is more specific than that of the method)

As given in here , a delegate can have more specific parameter types than its method target. For example the method targeted by the delegate expects an animal but the delegate input parameter is a dog.This is called contravariance.

using System;

namespace ContravarianceExample

{

    class Program

    {

        public delegate void ADelegate(Dog d);

        static void Main(string[] args)

        {

            ADelegate del = MyMethod;

            del(new Dog());//Dog is a specific kind of Animal

        }

        static void  MyMethod(Animal A)

        {

            Console.WriteLine(A.GetType());//Dog

        }

    }

    public class Animal

    {

    }

    public class Dog : Animal

    {

    }

}