I don't know what the error means but try a simple test. Copy the code below and see if you get the same error. This works on my machine.
Default.aspx <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http:// www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml";> <head runat="server"> <title></title> <script type="text/javascript"> function pageLoad() { } </script> </head> <body> <form id="form1" runat="server"> <div> <asp:ScriptManager ID="ScriptManager1" runat="server" /> <asp:UpdatePanel ID="UpdatePanel1" runat="server"> <ContentTemplate> Time 1:<asp:Label ID="lbl_time1" runat="server" /> <asp:Button ID="btn_updateTime" runat="server" Text="Update Time 1" onclick="btn_updateTime_Click" /> </ContentTemplate> </asp:UpdatePanel> Time 2:<asp:Label ID="lbl_time2" runat="server" /> </div> </form> </body> </html> Default.aspx.cs using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { lbl_time1.Text = DateTime.Now.ToLongTimeString(); lbl_time2.Text = DateTime.Now.ToLongTimeString(); } protected void btn_updateTime_Click(object sender, EventArgs e) { lbl_time1.Text = DateTime.Now.ToLongTimeString(); } }
