È possibile annullare il metodo asincrono nel controllo utente ASP.NET?

Ho utilizzato con successo il metodo async void nelle pagine Web Form di ASP.NET. Tuttavia, quando ho provato ad usare lo stesso metodo in un controllo utente web, e poi mettere questo controllo utente web a una pagina con async="true" impostazione, continuo a ricevere questo errore:È possibile annullare il metodo asincrono nel controllo utente ASP.NET?

An asynchronous operation cannot be started at this time. Asynchronous operations may only be started within an asynchronous handler or module or during certain events in the Page lifecycle. If this exception occurred while executing a Page, ensure that the Page is marked <%@ Page Async="true" %>.

Quindi la domanda è: si può void async il metodo deve essere utilizzato nel controllo utente Web e incorporato in una pagina modulo Web abilitata async?

fonte

2013-03-03 jack4it

È possibile avere metodi di controllo di chiamata asincrona se si trova su una pagina. Vedere l'esempio seguente:

Page.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Page.aspx.cs" Inherits="AsyncDEmo.Page" Async="true" %> 

<%@ Register Src="~/Control.ascx" TagPrefix="uc1" TagName="Control" %> 

<!DOCTYPE html> 

<html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
    <title></title> 
</head> 
<body> 
    <form id="form1" runat="server"> 
     <uc1:Control runat="server" id="Control" /> 
    </form> 
</body> 
</html>

codebehind di Page.aspx è vuoto

Control.ascx

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="Control.ascx.cs" Inherits="AsyncDEmo.Control" %> 

<span id="TaskMessage" runat="server"> 
     </span>

controllo Codebehind

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. 
     Page.RegisterAsyncTask(asyncTask1); 
     Page.RegisterAsyncTask(asyncTask2); 
     Page.RegisterAsyncTask(asyncTask3); 

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

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

SlowClass.cs

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. 
     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 = "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; 
     _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 += "AsyncTask failed to complete " + 
      "because it exceeded the AsyncTimeout parameter."; 
    } 
}

fonte

2013-03-26 21:25:39

È possibile annullare il metodo asincrono nel controllo utente ASP.NET?

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