Testing difference between sync and async

asynctest.cs

using System;
using System.Diagnostics;
using System.Net;
using System.Threading;
using System.Threading.Tasks;

namespace AsyncTest
{
    class Program
    {
        // result
        //10 11 13 15 17 19 3 5 7 9 12 4 2 6 8 14 16 0 18 1
        //0 2 4 12 10 16 14 8 18 1 6 5 3 13 7 17 11 9 15 19
        //Blocking:28270 msec; non-blocking: 1107 msec

        static void Main(string[] args)
        {
            var uri = "http://www.corebvba.be/blog";
            var n = 20;

            var blockingsw = new Stopwatch();
            
            blockingsw.Start();
            Parallel.For(0,n,i=> {
                var s = DownloadString(uri);
                Console.Write(i.ToString() + " ");
            });

            blockingsw.Stop();
            
            Console.WriteLine();

            var nonblockingsw = new Stopwatch();
            
            nonblockingsw.Start();
            Parallel.For(0,n,i=> {
                var s = DownloadString(uri);
                Console.Write(i.ToString()+" ");
            });
            
            nonblockingsw.Stop();
            
            Console.WriteLine();
            Console.WriteLine("Blocking:{0} msec; non-blocking: {1} msec", blockingsw.ElapsedMilliseconds, nonblockingsw.ElapsedMilliseconds);
            Console.ReadLine();
        }

        static string DownloadString(string uri)
        {
            return new WebClient().DownloadString(uri);
        }

        static string DownloadStringNonBlocking(string uri)
        {
            string result = null;
            var wc = new WebClient();
            Wait.Async(done =>
            {
                wc.DownloadStringCompleted+=(s,e)=> {  result = e.Result; done();};
                wc.DownloadStringAsync(new Uri(uri));
            });
            return result;
        }

        static class Wait
        {
            public static void Async(Action<Action> What)
            {
                var re = new ManualResetEvent(false);
                What(()=>re.Set());
                re.WaitOne();
            }
        }
    }
}

Paycento.API.Tasks.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace Paycento.API.Tasks
{
    public static class Wait
    {
        public static void Async(Action<Action> what)
        {
            var re = new ManualResetEvent(false);
            what(() => re.Set());
            re.WaitOne();
        }

        public static IEnumerable<T> AsAsync<T>(this IQueryable<T> what, System.Data.Linq.DataContext db)
        {
            var cmd = db.GetCommand(what) as System.Data.SqlClient.SqlCommand;
            if (cmd == null) return what;
            var conn = new System.Data.SqlClient.SqlConnection(db.Connection.ConnectionString + ";Asynchronous Processing=True;");
            conn.Open();
            cmd.Connection = conn;
            IAsyncResult res = null;
            Wait.Async(done =>
            {
                res = cmd.BeginExecuteReader(x => done(), null,System.Data.CommandBehavior.CloseConnection);
            });
            var rdr = cmd.EndExecuteReader(res);
            return db.Translate<T>(rdr);
        }
    }
}