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copied!<p>Looks like I can answer my own question. The user control should not be calling <code>Page.ExecuteRegisteredAsyncTasks</code>. By doing that, the control was adding the async task, running it, and waiting for it to complete.</p> <p>Instead, each instance of the user control should call only <code>Page.RegisterAsyncTask</code>. After each control instance has done this the page automatically calls <code>RegistereAsyncTask</code> running all three registered async tasks simultaniously.</p> <p>So here is the new user control:</p> <pre><code><%@ 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" /> </code></pre> <p>And the unchanged page that creates three instances of the control:</p> <pre><code><%@ 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> </code></pre>

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