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Polymorphism is a primary pillars of object oriented programming

Polymorphism allow you to invoke derived class methods through a base class reference during runtime. 

In the base class the method is declared as virtual and in the derived class we override the same method with “override keyword”.

The virtual keyword indicates, the method can be overridden in any derived class. 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using ConsoleApplication4;

namespace ConsoleApplication4
{

    /// <summary>
    /// Polymorphism example
    /// </summary>
    public class Employee
    {
        public string FirstName = “FN”;
        public string LastName = “LN”;
     

        public virtual void PrintFullName()
        {
            Console.WriteLine(FirstName + ” ” + LastName);
        }

    }

    public class FullTimeEmployee : Employee
    {
        public override void PrintFullName()
        {
            Console.WriteLine(FirstName + ” ” + LastName + “- FullTimeEmployee”);
        }
     
    }
    public class PartTimeEmployee : Employee
    {
        public override void PrintFullName()
        {
            Console.WriteLine(FirstName + ” ” + LastName + ” – PartTimeEmployee”);
        }
    }
    public class TemporaryEmployee : Employee
    {
        public override void PrintFullName()
        {
            Console.WriteLine(FirstName + ” ” + LastName + ” – TemporaryEmployee”);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
           Employee[] employees = new Employee[4];

           employees[0] = new FullTimeEmployee();
           employees[1] = new PartTimeEmployee();
           employees[2] = new TemporaryEmployee();
           employees[3] = new Employee();
           foreach (Employee e in employees)
           {
               e.PrintFullName();
               Console.ReadLine();
           }      

        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using ConsoleApplication4;

namespace ConsoleApplication4
{
    /// <summary>
    /// Base class Employee( Inheritance example)
    /// </summary>
    public class Employee
    {
        public string FirstName;
        public string LastName;
        public string Email;
   
        public void PrintFullName()
        {
            Console.WriteLine(FirstName + ” ” + LastName);
        }
    }
    /// <summary>
    /// Derived class inheriting Employee
    /// </summary>
    public class FullTimeEmployee : Employee
    {

      public  float YearlySalary;
    }
    /// <summary>
    /// Derived class inherting Employee
    /// </summary>

    public class PartTimeEmployee :  Employee
    {
     public  float HourlyRate;

    }
    class Program
    {
        static void Main(string[] args)
        {
            FullTimeEmployee FTE = new FullTimeEmployee();
            FTE.FirstName = “Mitali”;
            FTE.LastName = “Gurram”;
            FTE.Email = “malla.gurram@gmail.com”;
            FTE.YearlySalary = 100000;
            FTE.PrintFullName();
            Console.ReadLine();

            PartTimeEmployee PTE = new PartTimeEmployee();
            PTE.FirstName = “GMR”;
            PTE.LastName = “IT SOLUTIONS”;
            PTE.HourlyRate = 90;
            PTE.PrintFullName();
            Console.ReadLine();
        }

    }
}

Methods can have attributes, access modifiers, return types, method names, parameters and methods..

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

namespace ConsoleApplication3
{
    class Program
    {

        static void Main(string[] args)
        {
            Program p = new Program();
            p.EvenNumbers();
            int Sum = p.Add(10, 20);
            Console.WriteLine(“Sum={0}”, Sum);
            Console.ReadLine();
        }

        public int Add(int F ,int L)
        {
            return F + L;
        }
 
        public void EvenNumbers()
        {
            int start = 0;

            while (start <= 20)
            {
                Console.WriteLine(start);
                Console.ReadLine();
                start = start + 2;
             
            }
        }
    }
}