asp.net 2.0中實現非同步處理任務.

以下內容是在newsgroups中解決一個朋友的問題而寫的demo, 留下給自己做個備忘錄.

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關於PageAsyncTask在MSDN上的參考
ms-help://MS.VSCC.v90/MS.MSDNQTR.v90.en/fxref_system.web/html/08ffac7a-2c3c-27ee-1445-5284a226be38.htm

說明: 此頁面中, 在Page_Load方法中, 同時啟動4個較耗時的任務(線程), 讓它們並行的運行, 然後等待他們都運行完畢或逾時.

using System;

using System.Diagnostics;

using System.Threading;

using System.Web.Mvc;

using System.Web.UI;

namespace Portal.Views.Home

{

    public partial class Index : ViewPage

    {

        private string _asyncResult;

        private AsyncTaskDelegate _asyncTask;

        protected void Page_Load(object sender, EventArgs e)

        {

            Stopwatch sw = Stopwatch.StartNew();

            PageAsyncTask task1 =

                new PageAsyncTask(OnTaskBegin, OnTaskEnd, OnTaskTimeout, "A1", true);

            PageAsyncTask task2 =

                new PageAsyncTask(OnTaskBegin, OnTaskEnd, OnTaskTimeout, "B2", true);

            PageAsyncTask task3 =

                new PageAsyncTask(OnTaskBegin, OnTaskEnd, OnTaskTimeout, "C3", true);

            PageAsyncTask task4 =

                new PageAsyncTask(OnTaskBegin, OnTaskEnd, OnTaskTimeout, "D4", true);

            RegisterAsyncTask(task1);

            RegisterAsyncTask(task2);

            RegisterAsyncTask(task3);

            RegisterAsyncTask(task4);

            // By default, an asynchronous task will time out if it has not completed

            // within 45 seconds.

            AsyncTimeout = TimeSpan.FromSeconds(60);

            ExecuteRegisteredAsyncTasks();

            sw.Stop();

            // now, we can get the task result here.

            Response.Write(_asyncResult);

            Response.Write(sw.Elapsed.TotalSeconds);

        }

        private IAsyncResult OnTaskBegin(object sender,

                                         EventArgs e,

                                         AsyncCallback callback,

                                         object data)

        {

            _asyncTask = delegate(string text)

            {

                // TODO: add your async task here.

                string response =

                    string.Format("AsyncTask {0} started at: {1}. ", text, DateTime.Now);

                Thread.Sleep(TimeSpan.FromSeconds(10));

                response +=

                    string.Format("AsyncTask {0} ended at: {1}.\n", text, DateTime.Now);

                return response;

            };

            IAsyncResult result = _asyncTask.BeginInvoke((string) data, callback, data);

            return result;

        }

        private void OnTaskEnd(IAsyncResult ar)

        {

            _asyncResult += _asyncTask.EndInvoke(ar);

        }

        private void OnTaskTimeout(IAsyncResult ar)

        {

            _asyncResult = string.Format("AsyncTask {0} is time out.", ar.AsyncState);

        }

        #region Nested type: AsyncTaskDelegate

        protected delegate string AsyncTaskDelegate(string text);

        #endregion

    }

}

reference: http://msdn.microsoft.com/en-us/library/system.web.ui.pageasynctask(zh-cn).aspx