using System;

using System.Linq;

class Connection

{

    public int TotalOutstanding {get; set;}

    int _id = 0;

    static int count = 0;

    public Connection()

    {

        _id = ++count;

        Console.WriteLine("Connection() - id:{0}", _id);

    }

    public int Id

    {

        get {return _id;}

    }

}

​

class PoolService

{

    public static int POOL_SIZE = 100;

    private static readonly Object lockPookRoundRobin = new Object();

    private static Lazy<Connection>[] lazyConnection = null;

    //Static initializer to be executed once on the first call

    private static void InitConnectionPool()

    {

        lock (lockPookRoundRobin)

        {

            if (lazyConnection == null) {

                 lazyConnection = new Lazy<Connection>[POOL_SIZE];

            }

            for (int i = 0; i < POOL_SIZE; i++){

                if (lazyConnection[i] == null)

                    lazyConnection[i] = new Lazy<Connection>(() => new Connection());

            }

        }

    }

    private static Connection GetLeastLoadedConnection()

    {

        Lazy<Connection> lazyContext;

        //choose the least loaded connection from the pool

        var loadedLazys = lazyConnection.Where((lazy) => lazy.IsValueCreated);

        if(loadedLazys.Count()==lazyConnection.Count()){

            var minValue = loadedLazys.Min((lazy) => lazy.Value.TotalOutstanding);

            lazyContext = loadedLazys.Where((lazy) => lazy.Value.TotalOutstanding == minValue).First();

        }else{

            lazyContext = lazyConnection[loadedLazys.Count()];

        }

​

        lazyContext.Value.TotalOutstanding = lazyContext.Value.TotalOutstanding+1;

        return lazyContext.Value;

    }

    public Connection Connection

    {

        get

        {

            lock (lockPookRoundRobin)

            {

                return GetLeastLoadedConnection();

            }

        }

    }

    public PoolService()

    {

        InitConnectionPool();

    }

}

​

public class Program

{

    public static void Main()

    {

        PoolService pool = new PoolService();

        for(int i=0; i<PoolService.POOL_SIZE*2; i++){

            Connection connection = pool.Connection;

            Console.WriteLine("Main loaded Connection - id:{0} TotalOutstanding:{1}", connection.Id, connection.TotalOutstanding);

        }

    }

}

​