Contravariance Vs Covariance

Covariance Vs Contravariance

  static void Main()

  {

    ArgumentY oArgumentY = new ArgumentY();

    // In this case, the parameter to IncrA is ReturnX and the parameter to ChangeIt  is
    // ArgumentY.

    // Because of contravariance, the following line is OK.

    ChangeIt oChangeIt = IncrA;

    ReturnX oReturnX = oChangeIt(oArgumentY);

    Console.WriteLine("oReturnX: " + oReturnX.iValue);

    // In the next case, the return type of IncrB is ArgumentY and the return type of
    // ChangeIt is ReturnX.

    // Because of covariance, the following line is OK.

    oChangeIt = IncrB;

    oArgumentY = (ArgumentY) oChangeIt(oArgumentY);

    Console.WriteLine("oArgumentY: " + oArgumentY.iValue);

  }

}

The output from the program is shown here:

oReturnX: 1

oArgumentY: 1

Difference between Contravariance  Vs Covariance, real world scenarios and live code example on Contravariance  and Covariance, use of Contravariance  and Covariance in c # sharp dot .Net