Covariance And Contravariance In C# Languale

Introduction

Covariance and Contravariance of generic type parameters for interfaces and delegate types. covariance and contravariance enable to use reference conversion, and do not support value type. Covariance and contravariance bring flexibility to programming. Below in the given example show covariance and contravariance in delegate.

Example:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Covariance_and_contravariance_in_c_sharp

{

class Program

{

static object Get_Object()

{

return "return object";

}

static void Set_Object(object o)

{

}

static string Get_String()

{

return "Return String";

}

static void Set_String(string s)

{

}

static void Main(string[] args)

{

/* Covariance. A delegate, which is return type as object,

but we can assign a method, which returns a string.*/

Func<object> dgate1 = Get_String;

/* Contravariance. A delegate, which is a parameter type as string,

but we can assign a method that takes an object.*/

Action<string> dgate2 = Set_Object;

Console.WriteLine(Get_String());

Console.WriteLine(Get_Object());

Console.ReadLine();

}

Output: