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PageAsyncTask.TimeoutHandler Property

Gets the method to call when the task does not complete successfully within the time-out period.

Namespace:  System.Web.UI
Assembly:  System.Web (in System.Web.dll)

public EndEventHandler TimeoutHandler { get; }

Property Value

Type: System.Web.EndEventHandler
An EndEventHandler delegate that represents the method to call when the task does not complete successfully within the time-out period.

The TimeoutHandler delegate is set in the constructor.

The following code example registers three asynchronous tasks to a page and executes them in parallel. Each task calls a method that merely causes the thread to sleep for 5 seconds. A TimeoutHandler delegate is specified for each task.

<%@ Page Language="C#" Async="true" AsyncTimeout="35"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<script runat="server">

  protected void Page_Load(object sender, EventArgs e)

    // Define the asynchronuous task.
    Samples.AspNet.CS.Controls.SlowTask slowTask1 =    
      new Samples.AspNet.CS.Controls.SlowTask();
    Samples.AspNet.CS.Controls.SlowTask slowTask2 =
    new Samples.AspNet.CS.Controls.SlowTask();
    Samples.AspNet.CS.Controls.SlowTask slowTask3 =
    new Samples.AspNet.CS.Controls.SlowTask();

    PageAsyncTask asyncTask1 = new PageAsyncTask(slowTask1.OnBegin, slowTask1.OnEnd, slowTask1.OnTimeout, "Async1", true);
    PageAsyncTask asyncTask2 = new PageAsyncTask(slowTask2.OnBegin, slowTask2.OnEnd, slowTask2.OnTimeout, "Async2", true);
    PageAsyncTask asyncTask3 = new PageAsyncTask(slowTask3.OnBegin, slowTask3.OnEnd, slowTask3.OnTimeout, "Async3", true);

    // Register the asynchronous task.

    // Execute the register asynchronous task.

    TaskMessage.InnerHtml = slowTask1.GetAsyncTaskProgress()+ "<br />" + slowTask2.GetAsyncTaskProgress() + "<br />" + slowTask3.GetAsyncTaskProgress();


<html xmlns="" >
<head id="Head1" runat="server">
    <title>Asynchronous Task Example</title>
    <form id="form1" runat="server">
      <span id="TaskMessage" runat="server">

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

namespace Samples.AspNet.CS.Controls
    public class SlowTask
        private String _taskprogress;
        private AsyncTaskDelegate _dlgt;

        // Create delegate.
        protected delegate void AsyncTaskDelegate();

        public String GetAsyncTaskProgress()
            return _taskprogress;
        public void ExecuteAsyncTask()
            // Introduce an artificial delay to simulate a delayed 
            // asynchronous task.

        // Define the method that will get called to
        // start the asynchronous task.
        public IAsyncResult OnBegin(object sender, EventArgs e,
            AsyncCallback cb, object extraData)
            _taskprogress = "AsyncTask started at: " + DateTime.Now + ". ";

            _dlgt = new AsyncTaskDelegate(ExecuteAsyncTask);
            IAsyncResult result = _dlgt.BeginInvoke(cb, extraData);

            return result;

        // Define the method that will get called when
        // the asynchronous task is ended.
        public void OnEnd(IAsyncResult ar)
            _taskprogress += "AsyncTask completed at: " + DateTime.Now;

        // Define the method that will get called if the task
        // is not completed within the asynchronous timeout interval.
        public void OnTimeout(IAsyncResult ar)
            _taskprogress += "AsyncTask failed to complete " +
                "because it exceeded the AsyncTimeout parameter.";

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.