using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string source = @"    {

        ""lineups"": [

          {

            ""55"": {

              ""id"": ""55"",

              ""game_id"": ""1"",

              ""player_id"": ""55"",

              ""jersey_number"": ""78""

            },

            ""56"": {

              ""id"": ""56"",

              ""game_id"": ""1"",

              ""player_id"": ""56"",

              ""jersey_number"": ""77""

            },

            ""57"": {

              ""id"": ""57"",

              ""game_id"": ""1"",

              ""player_id"": ""57"",

              ""jersey_number"": ""76""

            }

        }]

 }";

        var l = Newtonsoft.Json.JsonConvert.DeserializeObject<Lineup>(source);

        Console.WriteLine(l.lineups[0].First().Value.ToString());

    }

}

​

public class Lineup

{

    public List<Dictionary<string,Player>> lineups;

}

​

public class Player

{

    public string id {get; set; }

    public string game_id { get; set;}

    public string player_id {get;set;}

    public string jersey_number {get;set;}

    public override string ToString()

    {

        return string.Format("id: {0}, game id: {1}, player id: {2}, jersey number: {3}",id,game_id,player_id,jersey_number);

    }

}