C#

WebClient wc = new WebClient();
wc.DownloadFile(@"http://aaa.uuu", @"D:\111.gig");

// Get the physical Path of the file(test.doc)
   string filepath = Server.MapPath("test.doc");
   // Create New instance of FileInfo class to get the properties of the file being downloaded
   FileInfo file = new FileInfo(filepath);
   // Checking if file exists
   if (file.Exists)
   {
    // Clear the content of the response
    Response.ClearContent();
    // LINE1: Add the file name and attachment, which will force the open/cance/save dialog to show, to the header
    Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);
    // Add the file size into the response header
    Response.AddHeader("Content-Length", file.Length.ToString());
    // Set the ContentType. function "ReturnExtension" return the proper content type and set it to the Response.ContentType property (not in this listing)
    Response.ContentType = ReturnExtension(file.Extension.ToLower());
    // Write the file into the response (TransmitFile is for ASP.NET 2.0. In ASP.NET 1.1 you have to use WriteFile instead)
    Response.TransmitFile(file.FullName);
    // End the response
    Response.End();
   }

class Program
    {
        static SerialPort sp = new SerialPort("COM8", 56000, Parity.None, 8);

        static void Main(string[] args)
        {
            if(!sp.IsOpen)
                sp.Open();
            sp.WriteLine("AT+DS44=?");
            sp.DataReceived += new SerialDataReceivedEventHandler(sp_DataReceived);

            ThreadStart ts = new ThreadStart(f);
            Thread t = new Thread(ts);
            t.Start();
        }

        static void f()
        {
            while (true) ;
        }

        static void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            Console.WriteLine("DataRecieved..............................");
            string str = sp.ReadLine();
            Console.WriteLine(str + "......................................");
        }
    }

private double timeOccurance2(string target)
      {
         string trial = string.Empty;
         double intialTime = DateTime.Now.ToOADate();
         Random rand = new Random();

         while (trial != target)
         {
             StringBuilder b = new StringBuilder();
             char[] ch = new char[target.Length];
             for (int i = 0; i < target.Length; i++)
            {
	    //here I have restricted possible characters to ~0-9
               ch[i] = Convert.ToChar(Convert.ToInt32(Math.Floor(10 * rand.NextDouble() + 48)));
            }

            for (int i = 0; i < target.Length; i++)
            {
               b.Append(ch[i].ToString());
            }

            trial = b.ToString();
         }

         double finalTime = DateTime.Now.ToOADate();
         return 24 * 60 * 60 * (finalTime - intialTime);
      }

private void button1_Click(object sender, EventArgs e)
     {
        for (int i = 1; i <= 40; i++)
        {
           BackgroundWorker Computation = new BackgroundWorker();
           Computation.DoWork += new DoWorkEventHandler(Computation_DoWork);
           Computation.RunWorkerCompleted += new RunWorkerCompletedEventHandler(Computation_RunWorkerCompleted);
           Computation.RunWorkerAsync();

     private void Computation_DoWork(object sender, DoWorkEventArgs e)
     {
        e.Result = timeOccurance2("123456").ToString();
     }

     private void Computation_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
     {
        richTextBox1.Text += (string)(e.Result);
        richTextBox1.Text += (char)(10);
     }