C# - Select many as the flatMap in Scala

If you are faimiar with Scala, you must have heard or used the function flatMap which is a very useful function that enable you to flat a collection. 

 

There is no such flatMap or Map method as in Scala, however, the C# linq has provide you with the necessary tools to allow you to do the flat map.

 

this has been discussed in this post "USE LINQ'S SELECTMANY METHOD TO "FLATTEN" COLLECTIONS", it has been discussed. 

 

Below I will save the droll and let's see the code. 

 

 

class League
  {
    public string Name { get; set; }
    public Team[] Teams { get; set; }
  }

  class Team
  {
    public string Name { get; set; } 
    public Player[] Players { get; set; }
    public int NumberOfWins { get; set; }
    public string HomeState { get; set; } 
  }

  class Player 
  {
    public string Name { get; set; }
    public int Age { get; set; } 
  }

  class Program
  {
    static void Main(string[] args)
    {
      var leagues = new List<League>
      {
        new League {
          Name = "AFC-West",
          Teams = new []{
            new Team {
              Name = "Chargers",
              NumberOfWins = 3,
              HomeState = "CA",
              Players = new [] {
                new Player { Name = "Rivers", Age = 30 },
                new Player { Name = "Tomlinson" , Age = 23},
                new Player { Name = "Gates" , Age = 18},
              }
            },
            new Team {
              Name = "Croncos",
              NumberOfWins = 2,
              HomeState = "LOS",
              Players = new [] {
                new Player { Name = "Culter", Age = 23 },
                new Player { Name = "Bailey", Age = 28 },
                new Player { Name = "Marshal", Age = 30 },
              }
            },
           }
         },
         new League {
           Name = "AFC-South",
           Teams = new [] {
            new Team {
              NumberOfWins = 1,
              Name = "Colts",
              HomeState = "NY",
              Players = new [] {
                new Player { Name = "Manning", Age = 31 },
                new Player { Name = "Bailey" , Age = 19},
                new Player { Name = "Vinatieri" , Age = 26},
              }
            },
           }
         },
        
      };


      var allTeams = from t in leagues.
                     SelectMany(l => l.Teams)
                     select t;

      var allPlayers = from p in leagues
                       .SelectMany(l => l.Teams)
                       .SelectMany(t => t.Players)
                       select p;

      var onlyYoungPlayers = from p in leagues
                             .SelectMany(l => l.Teams)
                             .SelectMany(t => t.Players)
                             where p.Age < 25
                             select p;

      var players = leagues.SelectMany(l => l.Teams)
                     .Where(t => t.NumberOfWins > 2)
                     .Where(p => p.HomeState == "CA")
                     .Select(p => p);

      var teamsAndTheirLeagues = from helper in leagues
                                 .SelectMany(l => l.Teams, (league, team) => new { league, team })
                                 where helper.team.Players.Length > 2
                                   && helper.league.Teams.Length < 10
                                   select new { LeagueID = helper.league.Name, Team = helper.team };
    }
  }