GenericMethod.cs

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

namespace Theory8
{
    class Customer
    {
        public int Id = 5;
    }
    class BaseClass<T> where T:class 
    {
         public virtual bool DoSomething(T obj)
         {
             Console.WriteLine("base");
             return true;
         }
    }

    class GenericMethod:BaseClass<Customer>
    {
        public override bool DoSomething(Customer obj)
        {
            Console.WriteLine("child => " + obj.Id);

            return true;
        }

        static void Main(string[] args)
        {
            Customer objCus = new Customer();
            GenericMethod obj = new GenericMethod();
            obj.DoSomething(objCus);
        }
    }
}