Demonstrates using the Enumerable.Select method with a partially applied function.

select-with-partial-application.cs

using System;
using System.Linq;
using System.Web.Script.Serialization;

class Main {
  public static void Main (string[] args) {
    string username = "George";
    string[] orderedHeroes = { "Luke Skywalker", "Han Solo", "Leia Organa", "Rey", "Finn", "Poe Dameron" };
    
    // Store CreateRanking in a variable as a first-class function.
    Func<string, string, int, Ranking> createRanking = CreateRanking;
    
    var partialCreateRanking = ApplyPartial(createRanking, username);
    Output(orderedHeroes.Select(partialCreateRanking));
    // Output: [
    //           {'username':'George','rebel':'Luke Skywalker','index':0},
    //           {'username':'George','rebel':'Han Solo','index':1},
    //           {'username':'George','rebel':'Leia Organa','index':2},
    //           {'username':'George','rebel':'Rey','index':3},
    //           {'username':'George','rebel':'Finn','index':4},
    //           {'username':'George','rebel':'Poe Dameron','index':5}
    //         ]
  }
  
  // This is Jon Skeet's implementation of partial application.
  static Func<T2, T3, TResult> ApplyPartial<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function, T1 arg1) {
      return (b, c) => function(arg1, b, c);
  }
  
  // Since C# doesn't have object literals, we need a class to represent a ranking.
  static Ranking CreateRanking(string username, string hero, int index) {
    return new Ranking(username, hero, index);
  }
  
  static void Output(IEnumerable<Ranking> rankings) {
    var json = new JavaScriptSerializer().Serialize(rankings.ToArray());
    Console.WriteLine(json);
  }
}

public class Ranking {
  public Ranking(string username, string hero, int index) {
    Username = username;
    Hero = hero;
    Index = index;
  }

  public string Username { get; private set; }
  public string Hero { get; private set; }
  public int Index { get; private set; }
}