protected void Page_Load(object sender, EventArgs e)
{
ScriptManager.RegisterStartupScript(BtnJs, this.GetType(), "alert", "<script>function
dis (){alert('這是調用寫在server的JS，如用Response.Write()是不能實現此效果的！！！ ');}</script>", false);

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true" >
</asp:ScriptManager>
<input id="BtnJs" type="button" value="CallServerJs" onclick="dis()" runat="server"/>
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" RenderMode="Block">
<ContentTemplate>
<asp:Button ID="Button6" runat="server" Text="Button" OnClientClick="dis()"/>
</ContentTemplate>
</asp:UpdatePanel>