webform1.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="work057.WebForm1" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title>Ajax控件实现UpateProgress进度条的示例</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:UpdateProgress ID="UpdateProgress1" runat="server">
                    <ProgressTemplate>
                        &nbsp;更新中......
                    </ProgressTemplate>
                </asp:UpdateProgress>
                <asp:Button ID="Button1" runat="server" Text="开始" OnClick="Button1_Click" />
                <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click" />
            </Triggers>
        </asp:UpdatePanel>
    </div>
    </form>
</body>
</html>

webform1.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace work057
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            Label1.Text = DateTime.Now.ToString();
            System.Threading.Thread.Sleep(3000);
        }
    }
}