Question

我正在尝试让用户控件异步工作，但无论我做什么，它都会继续同步工作。作为一个测试Web应用程序，我已经将它剥离到最低限度。这将是用户控件：

<%@ Control Language="C#" %>
<script runat="server">
    SqlConnection m_oConnection;
    SqlCommand    m_oCommand;

    void Page_Load(object sender, EventArgs e)
    {
        Trace.Warn("Page_Load");
        string strDSN = ConfigurationManager.ConnectionStrings["DSN"].ConnectionString + ";async=true";
        string strSQL = "waitfor delay '00:00:10'; select * from MyTable";

        m_oConnection = new SqlConnection(strDSN);
        m_oCommand = new SqlCommand(strSQL, m_oConnection);
        m_oConnection.Open();

        Page.RegisterAsyncTask(new PageAsyncTask(new BeginEventHandler(BeginHandler), new EndEventHandler(EndHandler), new EndEventHandler(TimeoutHandler), null, true));
        Page.ExecuteRegisteredAsyncTasks();
    }

    IAsyncResult BeginHandler(object src, EventArgs e, AsyncCallback cb, object state)
    {
        Trace.Warn("BeginHandler");
        return m_oCommand.BeginExecuteReader(cb, state);
    }

    void EndHandler(IAsyncResult ar)
    {
        Trace.Warn("EndHandler");
        GridView1.DataSource = m_oCommand.EndExecuteReader(ar);
        GridView1.DataBind();
        m_oConnection.Close();
    }

    void TimeoutHandler(IAsyncResult ar)
    {
        Trace.Warn("TimeoutHandler");
    }
</script>
<asp:gridview id="GridView1" runat="server" />

这将是我主持控件三次的页面：

<%@ page language="C#" trace="true" async="true" asynctimeout="60" %>
<%@ register tagprefix="uc" tagname="mycontrol" src="~/MyControl.ascx" %>
<html>
    <body>
        <form id="form1" runat="server">
            <uc:mycontrol id="MyControl1" runat="server" />
            <uc:mycontrol id="MyControl2" runat="server" />
            <uc:mycontrol id="MyControl3" runat="server" />
        </form>
    </body>
</html>

页面显示没有错误，但页面底部的跟踪显示每个控件实例是同步处理的。我究竟做错了什么？我缺少哪个配置设置？

Answer 1

看起来我可以回答我自己的问题。用户控件不应该调用Page.ExecuteRegisteredAsyncTasks。通过这样做，控件添加了异步任务，运行它，并等待它完成。

相反，用户控件的每个实例都应该只调用Page.RegisterAsyncTask。在每个控件实例完成此操作后，页面会自动调用RegistereAsyncTask同时运行所有三个已注册的异步任务。

所以这是新的用户控件：

<%@ Control Language="C#" %>
<script runat="server">
    SqlConnection m_oConnection;
    SqlCommand    m_oCommand;

    void Page_Load(object sender, EventArgs e)
    {
        Trace.Warn(ID, "Page_Load - " + Thread.CurrentThread.GetHashCode().ToString());
        string strDSN = ConfigurationManager.ConnectionStrings["DSN"].ConnectionString + ";async=true";
        string strSQL = "waitfor delay '00:00:10'; select * from TEProcessedPerDay where Date > dateadd(day, -90, getutcdate()) order by Date asc";

        m_oConnection = new SqlConnection(strDSN);
        m_oCommand = new SqlCommand(strSQL, m_oConnection);
        m_oConnection.Open();

        Page.RegisterAsyncTask(new PageAsyncTask(new BeginEventHandler(BeginHandler), new EndEventHandler(EndHandler), new EndEventHandler(TimeoutHandler), null, true));
    }

    IAsyncResult BeginHandler(object src, EventArgs e, AsyncCallback cb, object state)
    {
        Trace.Warn(ID, "BeginHandler - " + Thread.CurrentThread.GetHashCode().ToString());
        return m_oCommand.BeginExecuteReader(cb, state);
    }

    void EndHandler(IAsyncResult ar)
    {
        Trace.Warn(ID, "EndHandler - " + Thread.CurrentThread.GetHashCode().ToString());
        GridView1.DataSource = m_oCommand.EndExecuteReader(ar);
        GridView1.DataBind();
        m_oConnection.Close();
    }

    void TimeoutHandler(IAsyncResult ar)
    {
        Trace.Warn(ID, "TimeoutHandler - " + Thread.CurrentThread.GetHashCode().ToString());
    }
</script>
<asp:gridview id="GridView1" runat="server" />

创建三个控件实例的未更改页面：

<%@ page language="C#" async="true" trace="true" %>
<%@ register tagprefix="uc" tagname="mycontrol" src="~/MyControl.ascx" %>
<html>
    <body>
        <form id="form1" runat="server">
            <uc:mycontrol id="MyControl1" runat="server" />
            <uc:mycontrol id="MyControl2" runat="server" />
            <uc:mycontrol id="MyControl3" runat="server" />
        </form>
    </body>
</html>

Answer 2

如果我可以在上述帖子中添加一点内容，除非有令人信服的理由，否则我们不应明确调用ExecuteRegisteredAsyncTassk。注册异步任务后，ASP.NET框架将在页面生命周期的OnPrerender事件发生后立即执行所有这些任务。

使用ExecuteRegisteredAsyncTasks的示例可以是; 有时，在调用另一个异步任务之前，您可能需要确保完成多个异步操作。在这种情况下，使用ExecuteRegisteredAsyncTasks是合理的。

ASP.NET 2.0异步用户控件不起作用

2 个答案: