Detailed code explanation of C# HttpHandler asynchronous listening request

In server-side programming under high concurrency, when encountering performance bottlenecks, they are often caused by synchronization. When listening to HTTP requests, asynchronous is necessary.

Base class for asynchronously listening to HTTP requests:

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


namespace MyHandler
{
    public abstract class HttpAsyncHandler : IHttpAsyncHandler, IAsyncResult
    {
        public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {
            _callback = cb;
            _context = context;
            _completed = false;
            _state = this;


            ThreadPool.QueueUserWorkItem(new WaitCallback(DoProcess), this);
            return this;
        }


        public void EndProcessRequest(IAsyncResult result)
        {


        }


        public bool IsReusable
        {
            get { return false; }
        }


        public abstract void BeginProcess(HttpContext context);


        public void EndProcess()
        {
            //防止多次进行多次EndProcess


            if (!_completed)
            {
                try
                {
                    _completed = true;
                    if (_callback != null)
                    {
                        _callback(this);
                    }
                }
                catch (Exception) { }
            }
        }


        private static void DoProcess(object state)
        {
            HttpAsyncHandler handler = (HttpAsyncHandler)state;
            handler.BeginProcess(handler._context);
        }


        public void ProcessRequest(HttpContext context)
        {
            throw new NotImplementedException();
        }


        private bool _completed;
        private Object _state;
        private AsyncCallback _callback;
        private HttpContext _context;


        public object AsyncState
        {
            get { return _state; }
        }


        public WaitHandle AsyncWaitHandle
        {
            get { throw new NotImplementedException(); }
        }


        public bool CompletedSynchronously
        {
            get { return false; }
        }


        public bool IsCompleted
        {
            get { return _completed; }
        }
    }
}

Add TestHandler.cs:

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


namespace MyHandler
{
    public class TestHandler : HttpAsyncHandler
    {
        public override void BeginProcess(System.Web.HttpContext context)
        {
            try
            {
                StreamReader sr = new StreamReader(context.Request.InputStream);


                string reqStr = sr.ReadToEnd();
                context.Response.Write("get your input : " + reqStr + " at " + DateTime.Now.ToString());
            }
            catch (Exception ex)
            {
                context.Response.Write("exception eccurs ex info : " + ex.Message);
            }
            finally
            {
                EndProcess();////最后别忘了end
            }


        }
    }
}

Introduce MyHandler.dll into the site and modify WebConfig as follows:

<?xml version="1.0" encoding="utf-8"?>


<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.0"/>
    <pages validateRequest="false" controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID"/>
    <httpRuntime requestValidationMode="2.0"/>
    <customErrors mode="Off"/>
    <httpHandlers>
      <add verb="*" path="Test.aspx" type="MyHandler.TestHandler, MyHandler"/>
    </httpHandlers>
  </system.web>


</configuration>

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