Polymorphism is a fundamental concept in Object-Oriented Programming (OOP) that empowers a class to manifest multiple forms. It stands as one of the central tenets of OOP. This characteristic allows us to invoke methods and utilize derived classes through a reference variable of the base class during runtime. To achieve this, we use the "virtual" keyword to declare a method as virtual in the base class, and in the derived class, we employ the "override" keyword to provide a customized implementation of the same method.

using System

class Employee{ // parent class
 string FirstName;
 string LastName;
 string email;

public virtual void PrintName(){ //base class
Console.WriteLine(FirstName + " " + LastName)
}


public class FulltimeEmployee : Employee  // derived class
{
float YearlySalary;
public override void PrintName(){
Console.WriteLine(FirstName + " " + LastName + " " + "Fulltime Employee" )
}
}

public class ParttimeEmployee: Employee 
{
float HourlyRate;
public override void PrintName(){
Console.WriteLine(FirstName + " " + LastName + " " + "Parttime Employee" )
}
}

public class TempEmployee: Employee 
{
float HourlyRate;
public override void PrintName(){
Console.WriteLine(FirstName + " " + LastName + " " + "Temporay Employee" )
}
}

class Main {

public static void Main (){

Employee[] employees = new Employee[4];

employees[0] = new Employee();
employees[1] = new FulltimeEmployee();
employee[2] = new ParttimeEmployee();
employee[3] = new TempEmployee()

foreach (Employee e in employees){
e.PrintName() 
}

}
}