源码：
.aspx
1 <body>
2 <form id="form1" runat="server">
3 <p>
4 <asp:ScriptManager ID="ScriptManager1" runat="server">
5 </asp:ScriptManager>
6 <asp:UpdatePanel ID="UpdatePanel1" runat="server">
7 <ContentTemplate>
8 <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
9 <asp:Button ID="Button1" runat="server" Text="文件上传" onclick="Button1_Click" />
10 </ContentTemplate>
11 </asp:UpdatePanel>
12 <asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
13 <ProgressTemplate>文件上传中...<img src="images/wait.gif" / alt="上传中..."> </ProgressTemplate>
14 </asp:UpdateProgress>
15 </p>
16 </form>
17 </body>
.cs
1 public partial class _Default : System.Web.UI.Page
2 {
3 protected void Page_Load(object sender, EventArgs e)
4 {
5
6 }
7 protected void Button1_Click(object sender, EventArgs e)
8 {
9 System.Threading.Thread.Sleep(5000);
10 this.Label1.Text = "上传完成";
11
12 }
13 }
摘自 jory