Tip one to boost your asp.net application performance.

One of the secrets to producing scalable websites and services is to perform all your I/O operations asynchronously to avoid blocking threads.

When your thread issues a synchronous I/O request,the Windows kernel blocks the thread. This causes the thread pool to create a new thread, which allocates a lot of memory and wastes precious CPU time. Calling Async method and using C#’s async/await keywords allows your thread to return to the thread pool so it can be used for other things.

This reduces the resource consumption of your app, allowing it to use more memory and improving
response time to your clients.

using System;
using System.Net;
using System.Threading;
using System.Text;
using System.IO;

// The RequestState class passes data across async calls.
public class RequestState
{
   const int BufferSize = 1024;
   public StringBuilder RequestData;
   public byte[] BufferRead;
   public WebRequest Request;
   public Stream ResponseStream;
   // Create Decoder for appropriate enconding type.
   public Decoder StreamDecode = Encoding.UTF8.GetDecoder();
      
   public RequestState()
   {
      BufferRead = new byte[BufferSize];
      RequestData = new StringBuilder(String.Empty);
      Request = null;
      ResponseStream = null;
   }     
}

// ClientGetAsync issues the async request.
class ClientGetAsync 
{
   public static ManualResetEvent allDone = new ManualResetEvent(false);
   const int BUFFER_SIZE = 1024;

   public static void Main(string[] args) 
   {
      if (args.Length < 1) 
      {
         showusage();
         return;
      }

      // Get the URI from the command line.
      Uri httpSite = new Uri(args[0]);

      // Create the request object.
      WebRequest wreq = WebRequest.Create(httpSite);
        
      // Create the state object.
      RequestState rs = new RequestState();

      // Put the request into the state object so it can be passed around.
      rs.Request = wreq;

      // Issue the async request.
      IAsyncResult r = (IAsyncResult) wreq.BeginGetResponse(
         new AsyncCallback(RespCallback), rs);

      // Wait until the ManualResetEvent is set so that the application 
      // does not exit until after the callback is called.
      allDone.WaitOne();

      Console.WriteLine(rs.RequestData.ToString());
   }

   public static void showusage() {
      Console.WriteLine("Attempts to GET a URL");
      Console.WriteLine("\r\nUsage:");
      Console.WriteLine("   ClientGetAsync URL");
      Console.WriteLine("   Example:");
      Console.WriteLine("      ClientGetAsync http://www.contoso.com/");
   }

   private static void RespCallback(IAsyncResult ar)
   {
      // Get the RequestState object from the async result.
      RequestState rs = (RequestState) ar.AsyncState;

      // Get the WebRequest from RequestState.
      WebRequest req = rs.Request;

      // Call EndGetResponse, which produces the WebResponse object
      //  that came from the request issued above.
      WebResponse resp = req.EndGetResponse(ar);         

      //  Start reading data from the response stream.
      Stream ResponseStream = resp.GetResponseStream();

      // Store the response stream in RequestState to read 
      // the stream asynchronously.
      rs.ResponseStream = ResponseStream;

      //  Pass rs.BufferRead to BeginRead. Read data into rs.BufferRead
      IAsyncResult iarRead = ResponseStream.BeginRead(rs.BufferRead, 0, 
         BUFFER_SIZE, new AsyncCallback(ReadCallBack), rs); 
   }


   private static void ReadCallBack(IAsyncResult asyncResult)
   {
      // Get the RequestState object from AsyncResult.
      RequestState rs = (RequestState)asyncResult.AsyncState;

      // Retrieve the ResponseStream that was set in RespCallback. 
      Stream responseStream = rs.ResponseStream;

      // Read rs.BufferRead to verify that it contains data. 
      int read = responseStream.EndRead( asyncResult );
      if (read > 0)
      {
         // Prepare a Char array buffer for converting to Unicode.
         Char[] charBuffer = new Char[BUFFER_SIZE];
         
         // Convert byte stream to Char array and then to String.
         // len contains the number of characters converted to Unicode.
      int len = 
         rs.StreamDecode.GetChars(rs.BufferRead, 0, read, charBuffer, 0);

         String str = new String(charBuffer, 0, len);

         // Append the recently read data to the RequestData stringbuilder
         // object contained in RequestState.
         rs.RequestData.Append(
            Encoding.ASCII.GetString(rs.BufferRead, 0, read));         

         // Continue reading data until 
         // responseStream.EndRead returns –1.
         IAsyncResult ar = responseStream.BeginRead( 
            rs.BufferRead, 0, BUFFER_SIZE, 
            new AsyncCallback(ReadCallBack), rs);
      }
      else
      {
         if(rs.RequestData.Length>0)
         {
            //  Display data to the console.
            string strContent;                  
            strContent = rs.RequestData.ToString();
         }
         // Close down the response stream.
         responseStream.Close();         
         // Set the ManualResetEvent so the main thread can exit.
         allDone.Set();                           
      }
      return;
   }    
}