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Posted 5 Mar 2010

HTTP Push from SQL Server — Comet SQL

, 27 Nov 2012 CPOL
This article provides an example solution for presenting data in "real-time" from Microsoft SQL Server in an HTML browser. The article presents how to implement Comet functionality in ASP.NET and how to connect Comet with Query Notification from SQL Server.
// Copyright (c) 2010 Daniel Wojciechowski 
// E-mail: at daniel.wojciechowski

using System;
using System.Threading;
using System.Web;

namespace HttpPushFromMsSql
    public class CometAsyncResult:IAsyncResult
        private bool isCompleted = false;
        private bool completedSynchronously = false;

        /// <summary> Some information about situation on client
        /// side. Last seen record ID. This is example parameter
        /// for clarification what are we waiting for. </summary>
        public int LastRecId;

        public DateTime StartTime;
        public TimeSpan WaitTime;

        /// <summary> Callback that will be called when operation is completed
        /// (When we have notification about hanges, or timeout)</summary>
        public AsyncCallback Callback;

        public HttpContext Context;
        /// <summary> True when there is notification, False if timeout </summary>
        public bool Result;
        /// <summary>
        /// Default constructor. Can be used when request completed
        /// synchronously. In this case must set CompletedSynchronously 
        /// to true.
        /// </summary>
        public CometAsyncResult()

        public CometAsyncResult(HttpContext context, AsyncCallback asyncCallback, int waitTime, int lastRecId)
            Context = context;
            Callback = asyncCallback;
            StartTime = DateTime.Now;
            WaitTime = new TimeSpan(0, 0, waitTime);
            LastRecId = lastRecId; 

        public bool IsCompleted
            get { return isCompleted; }
            set { isCompleted = value; }
        public bool CompletedSynchronously
            get { return completedSynchronously; }
            set { completedSynchronously = value; }

        private readonly WaitHandle asyncWaitHandle = null;
        public WaitHandle AsyncWaitHandle { get { return asyncWaitHandle; } }

        private readonly object asyncState=null;
        public object AsyncState { get { return asyncState; } }


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About the Author

Software Developer
Poland Poland
I graduated from the Jagiellonian University. After defence of master thesis (link to presentation) I have started professional programming in C and C++ using OpenGL. After that, my Company gave me a chance to switch to .Net framework and C# and I have betrayed my passion for computer graphics. Now I'm C#, SQL and sometimes ASP.NET programmer.

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