using System;

using System.Threading.Tasks;

using System.Collections.Generic;

using System.Linq;

using System.Diagnostics;

public class Program

{

    public static void Main()

    {

        DoSomething();

    }

​

    private async static void DoSomething()

    {

        List<ILoader> loaderList = new List<ILoader>() { new LoaderA(), new LoaderB(), new LoaderC() };

        Stopwatch stopwatch = new Stopwatch();

        stopwatch.Start();

​

        Console.WriteLine("Loaders Registered:\n-------------------");

        foreach (var x in loaderList) Console.WriteLine("\t" + x.GetType().Name);

​

        Console.WriteLine("\nLoaders Executed:\n-----------------");

​

        var taskList = loaderList.Select(loader => {

            var loaderName = loader.GetType().Name;

​

            var myDictionaryTask = loader.LoadSomething(loaderName);

​

            if (myDictionaryTask.IsFaulted || myDictionaryTask.Result == null)

                Console.WriteLine("\t" + loaderName + ": returned null");

            else

                Console.WriteLine("\t" + loaderName + ": returned with " + myDictionaryTask.Result.Count() + " value");

​

            Console.WriteLine("");

            return myDictionaryTask;

        }).ToList();

​

        await Task.WhenAll(taskList);

        stopwatch.Stop();

        Console.WriteLine("\nTime elapsed: {0}", stopwatch.Elapsed);

    }

}

​

public interface ILoader

{

    Task<Dictionary<string, string>> LoadSomething(string keyValue);

}

​

public class LoaderA : ILoader

    {

        public async Task<Dictionary<string, string>> LoadSomething(string keyValue)

        {

            var dictionary = new Dictionary<string, string>()

            {

                { "AAA" , keyValue },

                { "BBB" , keyValue },

            };

            System.Threading.Thread.Sleep(1000);

​

            Console.WriteLine("\tLoaderA => Called Once");

​

            return dictionary;

        }

    }

​

    public class LoaderB : ILoader

    {

        public async Task<Dictionary<string, string>> LoadSomething(string keyValue)

        {

            Dictionary<string, string> dictionary = null;

            System.Threading.Thread.Sleep(1000);

​

            Console.WriteLine("\tLoaderB => Called Once");

​

            return dictionary;

        }

    }

​

    public class LoaderC : ILoader

    {

        public async Task<Dictionary<string, string>> LoadSomething(string keyValue)

        {

            var dictionary = new Dictionary<string, string>()

            {

                { "CCC" , keyValue },

                { "DDD" , keyValue },

                { "EEE" , keyValue },

            };

            System.Threading.Thread.Sleep(1000);

​

            Console.WriteLine("\tLoaderC => Called Once");

​

            return dictionary;

        }

    }