Generic Constraint Sample in C#

When creating a generic class, we saw that you can indicate that it would use a parameter type but you are not specifying the type of that parameter. You can put a restriction to indicate how the compiler should deal with the parameter. To create a constraint on a generic class, after the <TypeName> operator, type where TypeName: followed by the rule that the class must follow.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Generic
{
   class Program
   {
      static void Main(string[] args)
      {
         Employees<HR> HREmployees = new Employees<HR>();
         HREmployees.Add(new HR { Name = "HREmployee1" });
         HREmployees.Add(new HR { Name = "HREmployee2" });
         HREmployees.Add(new HR { Name = "HREmployee3" });
         HREmployees.Add(new HR { Name = "HREmployee4" });
         HREmployees.Add(new HR { Name = "HREmployee5" });
         Employees<Developer> DevEmployees = new Employees<Developer>();
         DevEmployees.Add(new Developer { dName = "DevEmployee1",platform="Dotnet" });
         DevEmployees.Add(new Developer { dName = "DevEmployee2",platform="Java"});
         DevEmployees.Add(new Developer { dName = "DevEmployee3",platform="Android"});
         DevEmployees.Add(new Developer { dName = "DevEmployee4",platform="IOS"});
         DevEmployees.Add(new Developer { dName = "DevEmployee5",platform="Database"});
         Console.WriteLine("********************************");
         Console.WriteLine(HREmployees.GetFirst().Name);
         Console.WriteLine(DevEmployees.GetFirst().dName);
         Console.WriteLine(DevEmployees.GetFirst().platform);
      }
   }
   public class Employees<T> where T : class
   {
      List<T> employees = new List<T>();
      public void Add(T item)
      {
         if (!employees.Contains(item))
         employees.Add(item);
      }
      public T GetFirst()
      {
         return (employees.Count > 0) ? employees[employees.Count-1] : null;
      }
   }
   public class HR
   {
      public string Name { get; set; }
   }
   public class Developer
   {
      public string dName { get; set; }
      public string platform { get; set; }
   }
}