<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager> //必须有且写在updatepanel前面
<asp:updatepanel runat="server" id="updatepanel1">
<contenttemplate>
<asp:textbox runat="server" id="txtname"></asp:textbox>
<asp:button runat="server" id="btn" text="检测" onclick="btn_click"></asp:button>
<asp:label runat="server" id="tip"></asp:label>
</contenttemplate>
</asp:updatepanel>