Contravariance, C#

Contravariance

//Title of this code
//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
	// This generic interface supports contravariance.

public interface IMyContraVarGenIF<in T>
	{

void Show(T obj);

}

// Implement the IMyContraVarGenIF interface.

class MyClass<T,V> : IMyContraVarGenIF<T> 
	{

public void Show(T x)
		{ 
			Console.WriteLine(x); 
		}
        
        public void Show2(V x)
		{ 
			Console.WriteLine(x); 
		}

}

// Create a simple class hierarchy.

class Alpha {

public override string ToString() 
		{

return "This is an Alpha object.";

}

// ...

}

class Beta : Alpha
	{

public override string ToString()
		{

return "This is a Beta object.";

}

// ...

}
	
	public class Program
	{
		public static void Main(string[] args)
		{

IMyContraVarGenIF<Alpha> AlphaRef = new MyClass<Alpha,Beta>();

IMyContraVarGenIF<Beta> BetaRef = new MyClass<Beta,Alpha>();

IMyContraVarGenIF<Beta> BetaRef2 = new MyClass<Alpha,Beta>();
            //IMyContraVarGenIF<Alpha> BetaRef12 = new MyClass<Beta>();

BetaRef.Show(new Beta());
            BetaRef2.Show(new Beta());
			AlphaRef.Show(new Alpha());

BetaRef = AlphaRef;

BetaRef.Show(new Beta());
		}
	}
}


run \| edit \| history \| help	0