如何實現vs.net控件updatePanel無刷新

　　頁面部分

 代碼如下:
<asp:ScriptManager ID="ScriptManager" runat="server">
</asp:ScriptManager>
<h>
使用VS控件updatePanel實現無刷新
</h>
<p>
<asp:UpdatePanel ID="UpdatePanel" RenderMode="Block" UpdateMode="Conditional" runat="server">
<ContentTemplate>
點擊按鈕從服務器獲取當前時間<asp:TextBox ID="txtTime" runat="server"></asp:TextBox>
<asp:Button ID="btn" runat="server" Text="Button" onclick="btn_Click" />
</ContentTemplate>
<Triggers>
<%<asp:PostBackTrigger ControlID="btn" />%>
<asp:AsyncPostBackTrigger ControlID="btn"/>
</Triggers>
</asp:UpdatePanel>
</p>

　　
後台代碼

代碼如下:
protected void btn_Click(object sender EventArgs e)
{
txtTimeText = DateTimeNowToString();
}
From:http://tw.wingwit.com/Article/program/net/201311/14324.html