Virtual-override example.

1.Base class

  public class BaseClass
    {
       public virtual int add()
        {
            return 10;
        }
              
    }

2.Child Class

  public class ChildClass : BaseClass
    {
        public override int add()
        {
            base.add();
            return 12;
        }

    }

2.Calling the add() method in main()

 class Program
    {
        static void Main(string[] args)
        {
            //Creating ChildClass object 
            ChildClass childObj = new ChildClass();
            //Calling the ChildClass add method 
            Console.WriteLine(childObj.add());

            Console.ReadKey();
        }
    }