如何使用多线程更新标签文本[重复]

Question

可能重复：
How to update aspx page while using Multithreading

我想在 asp.net 网站中执行多线程时更新 Label 文本，我的代码工作正常，但它没有更新 Label 文本。当我调试它时，它工作正常，并在后面的代码中更新标签的值，但它不会影响字体屏幕（页面）。我的代码是：

.ASPX 代码：

<form id="form1" runat="server">
    <div style="width:100%; text-align:center;">
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
        <br /> <br /> <br /> <br /> <br />
        Thread 1: <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>  <br /><br />
        Thread 2: <asp:Label ID="Label2" runat="server" Text="Label"></asp:Label> <br /><br />
        Thread 3: <asp:Label ID="Label3" runat="server" Text="Label"></asp:Label> <br /><br />
        Thread 4: <asp:Label ID="Label4" runat="server" Text="Label"></asp:Label> <br /><br />
        Thread 5: <asp:Label ID="Label5" runat="server" Text="Label"></asp:Label> <br /><br />
        Thread 6: <asp:Label ID="Label6" runat="server" Text="Label"></asp:Label> <br /><br />
        Thread 7: <asp:Label ID="Label7" runat="server" Text="Label"></asp:Label> <br />
            </ContentTemplate>
        </asp:UpdatePanel>
    </div>
    </form>

.CS 代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Threading;
using System.Runtime.Remoting.Messaging;

public partial class Default_test : System.Web.UI.Page
{
    public delegate string Delg_Method1(int a, int b);
    public delegate string Delg_Method2(int a, int b);
    public delegate string Delg_Method3(int a, int b);
    public delegate string Delg_Method4(int a, int b);
    public delegate string Delg_Method5(int a, int b);
    public delegate string Delg_Method6(int a, int b);
    public delegate string Delg_Method7(int a, int b);
    protected void Page_Load(object sender, EventArgs e)
    {
        Label1.Text = "Waiting ...";
        Label2.Text = "Waiting ...";
        Label3.Text = "Waiting ...";
        Label4.Text = "Waiting ...";
        Label5.Text = "Waiting ...";
        Label6.Text = "Waiting ...";
        Label7.Text = "Waiting ...";
        callingAsynchMultiThreads();

    }

    #region Threads

    public void callingAsynchMultiThreads()
    {

        AsyncCallback method1Callback = new AsyncCallback(Method1Complete);
        Delg_Method1 dlg_call1 = new Delg_Method1(Load_Method1);
        IAsyncResult iar1 = dlg_call1.BeginInvoke(1, 0, method1Callback, null);

        AsyncCallback method2Callback = new AsyncCallback(Method2Complete);
        Delg_Method2 dlg_call2 = new Delg_Method2(Load_Method2);
        IAsyncResult iar2 = dlg_call2.BeginInvoke(1, 1, method2Callback, null);

        AsyncCallback method3Callback = new AsyncCallback(Method3Complete);
        Delg_Method3 dlg_call3 = new Delg_Method3(Load_Method3);
        IAsyncResult iar3 = dlg_call3.BeginInvoke(1, 2, method3Callback, null);

        AsyncCallback method4Callback = new AsyncCallback(Method4Complete);
        Delg_Method4 dlg_call4 = new Delg_Method4(Load_Method4);
        IAsyncResult iar4 = dlg_call4.BeginInvoke(1, 3, method4Callback, null);

        AsyncCallback method5Callback = new AsyncCallback(Method5Complete);
        Delg_Method5 dlg_call5 = new Delg_Method5(Load_Method5);
        IAsyncResult iar5 = dlg_call5.BeginInvoke(1, 4, method5Callback, null);

        AsyncCallback method6Callback = new AsyncCallback(Method6Complete);
        Delg_Method6 dlg_call6 = new Delg_Method6(Load_Method6);
        IAsyncResult iar6 = dlg_call6.BeginInvoke(1, 5, method6Callback, null);

        AsyncCallback method7Callback = new AsyncCallback(Method7Complete);
        Delg_Method7 dlg_call7 = new Delg_Method7(Load_Method7);
        IAsyncResult iar7 = dlg_call7.BeginInvoke(1, 6, method7Callback, null);


    }
    public string Load_Method1(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }
    public string Load_Method2(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }
    public string Load_Method3(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }
    public string Load_Method4(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }
    public string Load_Method5(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }
    public string Load_Method6(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }
    public string Load_Method7(int a, int b)
    {
        int temp = a + b;
        return temp.ToString();
    }

    public void Method1Complete(IAsyncResult ar)
    {
        Thread.Sleep(500);
        Delg_Method1 dlgM1 = (Delg_Method1)((AsyncResult)ar).AsyncDelegate;
        //dlgM1.EndInvoke(ar);
        Label1.Text = dlgM1.EndInvoke(ar).ToString();


    }
    public void Method2Complete(IAsyncResult ar)
    {
        Thread.Sleep(1000);
        Delg_Method2 dlgM2 = (Delg_Method2)((AsyncResult)ar).AsyncDelegate;
        //dlgM2.EndInvoke(ar);
        Label2.Text = dlgM2.EndInvoke(ar).ToString();
    }
    public void Method3Complete(IAsyncResult ar)
    {
        Thread.Sleep(1500);
        Delg_Method3 dlgM3 = (Delg_Method3)((AsyncResult)ar).AsyncDelegate;
        //dlgM3.EndInvoke(ar);
        Label3.Text = dlgM3.EndInvoke(ar).ToString();
    }
    public void Method4Complete(IAsyncResult ar)
    {
        Thread.Sleep(2000);
        Delg_Method4 dlgM4 = (Delg_Method4)((AsyncResult)ar).AsyncDelegate;
        //dlgM4.EndInvoke(ar);
        Label4.Text = dlgM4.EndInvoke(ar).ToString();
    }
    public void Method5Complete(IAsyncResult ar)
    {
        Thread.Sleep(2500);
        Delg_Method5 dlgM5 = (Delg_Method5)((AsyncResult)ar).AsyncDelegate;
        //dlgM5.EndInvoke(ar);
        Label5.Text = dlgM5.EndInvoke(ar).ToString();
    }
    public void Method6Complete(IAsyncResult ar)
    {
        Thread.Sleep(3000);
        Delg_Method6 dlgM6 = (Delg_Method6)((AsyncResult)ar).AsyncDelegate;
        //dlgM6.EndInvoke(ar);
        Label6.Text = dlgM6.EndInvoke(ar).ToString();
    }
    public void Method7Complete(IAsyncResult ar)
    {
        Thread.Sleep(3500);
        Delg_Method7 dlgM7 = (Delg_Method7)((AsyncResult)ar).AsyncDelegate;
        //dlgM7.EndInvoke(ar);
        Label7.Text = dlgM7.EndInvoke(ar).ToString();

    }


    #endregion

}

Answer 1

这是因为页面生命周期已经结束，并且页面在线程完成更新其控件之前渲染/发送到浏览器。在调试期间，您可以看到线程完成了它们的工作，但正在更改已经发送到浏览器的标签。

一旦页面被发送到浏览器，服务器就不能在没有客户端请求“新版本”的情况下向客户端发送新版本。解决此问题的一种可能方法是让页面通过 AJAX / JavaScript 或类似方法不断检查更新，以便在线程完成时显示新值。

一个非常使用UpdatePanel每5秒更新一次页面的简单示例是：

网页 (ASPX)

<asp:UpdatePanel ID="updateView" runat="server" >
<ContentTemplate>

    <!-- Refresh the page automatically -->
    <asp:Timer ID="timAutoRefresh" runat="server" Interval="5000" OnTick="OnRefresh_Tick" />

</ContentTemplate>
</asp:UpdatePanel>

代码隐藏 (.cs)

protected void OnRefresh_Tick(object sender, EventArgs e)
{       
    // Check values and update page...
}

还有其他方法，这是一个非常简单的示例。您应该将标签添加到与计时器相同的 UpdatePanel 中并更改 UpdatePanel，使其仅更新自身以最小化回发等。