using System;

using System.Threading;

using System.Threading.Tasks;

​

class Program

{

      static void Main(string[] args)

     {

         SaySomething(args[0]);

         Console.WriteLine(result);

     }

​

     static async Task SaySomething(string key)

     {

         switch (key)

         {

             case "1":

                 await Task.Delay(5);

                 result = "1";

                 break;

             case "2":

                 Thread.Sleep(5);

                 result = "2";

                 break;

             case "3":

                 await Task.FromResult(5);

                 result = "3";

                 break;

             case "4":

                 var thread = new Thread(() =>

                 {

                     result = "Nope";

                 });

                 thread.Start();

                 result = "4";

                 break;

             case "5":

                 var sum = 0;

                 Parallel.For(0, 3, i=>

                 {

                     Thread.Sleep(50);

                     sum += i;

                 });

                 result = sum.ToString();

                 break;

         }

     }

​

        private static string result;

}

​