Page.ExecuteRegisteredAsyncTasks Method

Definition

Avvia l'esecuzione di un'attività asincrona.Starts the execution of an asynchronous task.

public:
 void ExecuteRegisteredAsyncTasks();
public void ExecuteRegisteredAsyncTasks ();
member this.ExecuteRegisteredAsyncTasks : unit -> unit
Public Sub ExecuteRegisteredAsyncTasks ()

Exceptions

Si è verificata un'eccezione nell'attività asincrona.There is an exception in the asynchronous task.

Examples

Nell'esempio di codice riportato di seguito viene illustrato l'utilizzo della proprietà AsyncTimeout con i metodi ExecuteRegisteredAsyncTasks e RegisterAsyncTask.The following code example demonstrates the use of the AsyncTimeout property with the ExecuteRegisteredAsyncTasks and RegisterAsyncTask methods. Si noti l'uso dei gestori di inizio, fine e timeout.Note the use of beginning, ending, and time-out handlers. Nell'esempio viene introdotto un ritardo artificiale per dimostrare la situazione di un'attività asincrona che supera il tempo assegnato per l'attività, come specificato nella proprietà AsyncTimeout.In the example, an artificial delay is introduced to demonstrate the situation of an asynchronous task exceeding the allotted time for the task as specified in the AsyncTimeout property. In uno scenario reale, un'attività asincrona può essere usata per eseguire chiamate di database o la generazione di immagini, ad esempio, e il gestore di timeout fornisce un calo di qualità se l'attività non viene eseguita in un periodo di tempo specificato.In a real-world scenario, an asynchronous task could be used to perform database calls or image generation, for example, and the time-out handler provides graceful degradation if the task is not performed in a specified amount of time.

<%@ Page Language="C#" AsyncTimeout="2"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  protected void Page_Load(object sender, EventArgs e)
  {
    // Define the asynchronuous task.
    Samples.AspNet.CS.Controls.MyAsyncTask mytask =    
      new Samples.AspNet.CS.Controls.MyAsyncTask();
    PageAsyncTask asynctask = new PageAsyncTask(mytask.OnBegin, mytask.OnEnd, mytask.OnTimeout, null);

    // Register the asynchronous task.
    Page.RegisterAsyncTask(asynctask);
      
    // Execute the register asynchronous task.
    Page.ExecuteRegisteredAsyncTasks();

    TaskMessage.InnerHtml = mytask.GetAsyncTaskProgress();

  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Asynchronous Task Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <span id="TaskMessage" runat="server">
      </span>
    </div>
    </form>
</body>
</html>
<%@ Page Language="VB" AsyncTimeout="2"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    
    ' Define the asynchronuous task.
    Dim mytask As New Samples.AspNet.VB.Controls.MyAsyncTask()
    Dim asynctask As New PageAsyncTask(AddressOf mytask.OnBegin, AddressOf mytask.OnEnd, AddressOf mytask.OnTimeout, DBNull.Value)

    ' Register the asynchronous task.
    Page.RegisterAsyncTask(asynctask)
      
    ' Execute the register asynchronous task.
    Page.ExecuteRegisteredAsyncTasks()

    TaskMessage.InnerHtml = mytask.GetAsyncTaskProgress()
    
  End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Asynchronous Task Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <span id="TaskMessage" runat="server">
      </span>
    </div>
    </form>
</body>
</html>
using System;
using System.Web;
using System.Web.UI;
using System.Threading;

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

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

        public String GetAsyncTaskProgress()
        {
            return _taskprogress;
        }
        public void DoTheAsyncTask()
        {
            // Introduce an artificial delay to simulate a delayed 
            // asynchronous task. Make this greater than the 
            // AsyncTimeout property.
            Thread.Sleep(TimeSpan.FromSeconds(5.0));
        }

        // Define the method that will get called to
        // start the asynchronous task.
        public IAsyncResult OnBegin(object sender, EventArgs e,
            AsyncCallback cb, object extraData)
        {
            _taskprogress = "Beginning async task.";

            _dlgt = new AsyncTaskDelegate(DoTheAsyncTask);
            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 = "Asynchronous task completed.";
            _dlgt.EndInvoke(ar);
        }

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

Namespace Samples.AspNet.VB.Controls

    Public Class MyAsyncTask

        Private _taskprogress As String
        Private _dlgt As AsyncTaskDelegate

        ' Create delegate.
        Delegate Function AsyncTaskDelegate()

        Public Function GetAsyncTaskProgress() As String
            Return _taskprogress
        End Function

        Public Function DoTheAsyncTask()

            ' Introduce an artificial delay to simulate a delayed 
            ' asynchronous task. Make this greater than the 
            ' AsyncTimeout property.
            Thread.Sleep(TimeSpan.FromSeconds(5.0))

        End Function


        ' Define the method that will get called to
        ' start the asynchronous task.
        Public Function OnBegin(ByVal sender As Object, ByVal e As EventArgs, ByVal cb As AsyncCallback, ByVal extraData As Object) As IAsyncResult

            _taskprogress = "Beginning async task."

            Dim _dlgt As New AsyncTaskDelegate(AddressOf DoTheAsyncTask)
            Dim result As IAsyncResult = _dlgt.BeginInvoke(cb, extraData)
            Return result

        End Function 'OnBegin

        ' Define the method that will get called when
        ' the asynchronous task is ended.
        Public Sub OnEnd(ByVal ar As IAsyncResult)

            _taskprogress = "Asynchronous task completed."
            _dlgt.EndInvoke(ar)

        End Sub

        ' Define the method that will get called if the task
        ' is not completed within the asynchronous timeout interval.
        Public Sub OnTimeout(ByVal ar As IAsyncResult)

            _taskprogress = "Ansynchronous task failed to complete because " & _
            "it exceeded the AsyncTimeout parameter."

        End Sub

    End Class

End Namespace

Remarks

Definire un'attività asincrona usando la classe PageAsyncTask.Define an asynchronous task using the PageAsyncTask class. Dopo che l'attività è stata definita e viene registrata con la pagina usando il metodo RegisterAsyncTask, è possibile richiamare il metodo ExecuteRegisteredAsyncTasks per avviare l'attività asincrona.After the task is defined, and is registered with the page using the RegisterAsyncTask method, the ExecuteRegisteredAsyncTasks method can be invoked to begin the asynchronous task.

Il metodo ExecuteRegisteredAsyncTasks viene chiamato automaticamente nel punto dell'elaborazione della pagina quando vengono richiamate eventuali attività asincrone registrate, per una pagina non asincrona.The ExecuteRegisteredAsyncTasks method is automatically called at the point in the page processing when any registered asynchronous tasks, if they exist, are invoked for a non-asynchronous page. Questa chiamata automatica a ExecuteRegisteredAsyncTasks si verifica immediatamente prima dell'evento PreRenderComplete.This automatic call to ExecuteRegisteredAsyncTasks occurs just before the PreRenderComplete event. Chiamare il metodo ExecuteRegisteredAsyncTasks per le attività che si desidera richiamare in momenti diversi dalla chiamata automatica a questo metodo.Call the ExecuteRegisteredAsyncTasks method for tasks you want to be invoked at times other than the automatic call to this method. Si noti che le attività asincrone verranno eseguite solo una volta, anche se ExecuteRegisteredAsyncTasks può essere chiamato più di una volta.Note, asynchronous tasks will be executed only once even though ExecuteRegisteredAsyncTasks may be called more than once.

La proprietà AsyncTimeout viene reimpostata a ogni chiamata al metodo ExecuteRegisteredAsyncTasks.The AsyncTimeout property is reset on every call to the ExecuteRegisteredAsyncTasks method. L'ultimo valore del AsyncTimeout prima di richiamare il metodo ExecuteRegisteredAsyncTasks ha la precedenza.The last value of the AsyncTimeout prior to invoking the ExecuteRegisteredAsyncTasks method takes precedence. Se un'attività asincrona impiega più di AsyncTimeout, le attività successive richiamate durante il ExecuteRegisteredAsyncTasks periodo di tempo vengono richiamate immediatamente.If an asynchronous task takes more than the AsyncTimeout, subsequent tasks invoked during that ExecuteRegisteredAsyncTasks call are timed out immediately.

Applies to

See also