Group

GroupbBy is defferd execution ToLookup is immidate execution

using System;  
using System.Collections;  
using System.Collections.Generic;  
using System.Linq;  
  
namespace LinqProject  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            List<Team>  teams = new List<Team>()  
            {  
                new Team {  Name="Perpolis" , County = " Iran"},  
                new Team {  Name="Esteghlal" , County = " Iran"},  
                new Team {  Name="psg" , County = " France"},  
                new Team {  Name="Arsenal" , County = " England"},  
                new Team {  Name="Everton " , County = " England"},  
                new Team {  Name=" Manchester City " , County = " England"},  
            };  
  
            var result = teams.GroupBy(p => p.County);  
  
            foreach (var country in result)  
            {                Console.WriteLine("County Group: {0}", country.Key);  
  
                foreach (var item in country)  
                {                    Console.WriteLine("Team Name: {0}", item.Name);  
                }                Console.WriteLine("______________________");  
  
            }              
              
var result2 = teams.ToLookup(p => p.County);  
  
            foreach (var country in result2)  
            {                Console.WriteLine("County Group: {0}", country.Key);  
  
                foreach (var item in country)  
                {                    Console.WriteLine("Team Name: {0}", item.Name);  
                }                Console.WriteLine("______________________");  
  
            }  
  
            Console.ReadLine();  
        }  
  
          }  
  
  
      
  
  
    public class Team  
    {  
        public string Name { get; set; }  
        public string County { get; set; }  
    }  
}

LINQ