using System;

public class Program

{

      public class test

      { }

      public class test2:test

      { }

      public static void Main()

      {

         DDoSomething<test> doSomething = DoSomething;

​

         var obj = new test2();

​

         doSomething(obj);

      }

​

      public delegate void DDoSomething<in A>(A str);

​

      public static void DoSomething(test str)

      {

​

      }

​

}