class AsyncIndexer

    {

        public static int debugPause;

        Queue<string> urlQueue = new Queue<string>();

        public int QueueSize { get { return urlQueue.Count; } }

        bool busy = false;

        static AsyncIndexer instance = null;

        public static AsyncIndexer GetInstance()

        {

            if (instance == null) instance = new AsyncIndexer();

            return instance;

        }

        delegate void IndexDelegate(Keyoti.SearchEngine.Configuration config);

        public void QueueForIndexing(string documentURL, Keyoti.SearchEngine.Configuration config)

        {

            //add new URL to queue

            urlQueue.Enqueue(documentURL); 

            IndexDelegate indexDelegate = new IndexDelegate(delegate(Keyoti.SearchEngine.Configuration configuration)

            {

                //do indexing work here

                if (!busy)

                {

                    busy = true;

                    //this outer 'while' just takes care of anything added to the queue during the documentIndex.Close() call.

                    while (urlQueue.Count > 0)

                        ProcessQueueItems(configuration);

                    busy = false;

                }               

            });

            IAsyncResult ar = indexDelegate.BeginInvoke(config, new AsyncCallback(MyCallback), null);

        }

        void ProcessQueueItems(Keyoti.SearchEngine.Configuration configration)

        {

            Keyoti.SearchEngine.Index.DocumentIndex documentIndex = new Keyoti.SearchEngine.Index.DocumentIndex(configration);

            try

            {

                //while anything is waiting in the queue

                while (urlQueue.Count > 0)

                {

                    documentIndex.AddDocument(new Keyoti.SearchEngine.Documents.Document(urlQueue.Dequeue(), configration));

                    System.Threading.Thread.Sleep(debugPause);

                }

            }

            finally

            {

                documentIndex.Close();

            }

        }

        void MyCallback(IAsyncResult ar)

        {

            AsyncResult aResult = (AsyncResult)ar;

            IndexDelegate idxDelegate = (IndexDelegate)aResult.AsyncDelegate;

            idxDelegate.EndInvoke(ar);

        }

    }

2. Use it like this:

AsyncIndexer.GetInstance().QueueForIndexing(documentURL, config);

It should be 'fire and forget' - so you call it, and the ASP.NET page returns immediately. You can get the queue size like this

AsyncIndexer.GetInstance().QueueSize

Here's a complete test example – set the 'debugPause' to allow time for the queue to build up (otherwise it's too quick to test) – it’s currently 7 seconds for each document!

ASPX

<asp:TextBox ID="tb1" runat="server" Width="393px" Text="http://"/>

    <asp:Button ID="indexBt" runat="server" Text="Index Now"

        onclick="indexBt_Click" />

        <asp:Label runat="server" ID="label1"></asp:Label>

CODEBEHIND

        protected void Page_Load(object sender, EventArgs e)

        {

            AsyncIndexer.debugPause = 7000;

        }

        delegate void IndexDelegate(string indexDirectory, Keyoti.SearchEngine.Configuration config);

        protected void indexBt_Click(object sender, EventArgs e)

        {

            string documentURL = tb1.Text;

            Keyoti.SearchEngine.Configuration config = new Keyoti.SearchEngine.Configuration();

            config.IndexDirectory = "c:\\d\\6";

            AsyncIndexer.GetInstance().QueueForIndexing(documentURL, config);

            label1.Text = "Indexing... queue size is " + AsyncIndexer.GetInstance().QueueSize;

        }