Group all employees by department in CSharp

   /*w  w w .j a  va  2 s  .  c  o m*/

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


class Employee : IComparable<Employee>
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Department { get; set; }
    public int Id { get; set; }

    public override string ToString()
    {
        return String.Format("Id: {0}, Name: {1} {2}, Dept: {3}", this.Id, this.FirstName, this.LastName, this.Department);
    }
    int IComparable<Employee>.CompareTo(Employee other)
    {
        if (other == null)
            return 1;

        if (this.Id > other.Id)
            return 1;

        if (this.Id < other.Id)
            return -1;

        return 0;
    }
}

class Program
{
    static void Main()
    {
        List<Employee> empTree = new List<Employee>();
        empTree.Add(new Employee { Id = 1, FirstName = "Janet", LastName = "Gates", Department = "IT" });
        empTree.Add(new Employee { Id = 2, FirstName = "O", LastName = "G", Department = "Marketing" });
        empTree.Add(new Employee { Id = 4, FirstName = "K", LastName = "H", Department = "IT" });
        empTree.Add(new Employee { Id = 6, FirstName = "L", LastName = "H", Department = "Sales" });
        empTree.Add(new Employee { Id = 3, FirstName = "E", LastName = "L", Department = "Sales" });
        empTree.Add(new Employee { Id = 5, FirstName = "D", LastName = "L", Department = "Marketing" });

        var employeesByDept = from e in empTree group e by e.Department;

        foreach (var dept in employeesByDept)
        {
            Console.WriteLine("Department: {0}", dept.Key);
            foreach (var emp in dept)
            {
                Console.WriteLine("\t{0} {1}", emp.FirstName, emp.LastName);
            }
        }
    }
}