vs新增ajax无刷新控件例子.

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server"   >
        <ContentTemplate>
            <asp:DropDownList ID="ddl1" runat="server"
                onselectedindexchanged="ddl1_SelectedIndexChanged" AutoPostBack="True">
            </asp:DropDownList>
            <asp:UpdatePanel ID="UpdatePanel2" runat="server" RenderMode="Inline"
                UpdateMode="Conditional"   >
                <ContentTemplate>
                    <asp:DropDownList ID="ddl2" runat="server">
                    </asp:DropDownList>
                    <asp:DropDownList ID="ddl3" runat="server">
                    </asp:DropDownList>
                </ContentTemplate>
                <Triggers>
                    <asp:AsyncPostBackTrigger ControlID="ddl2" />
                </Triggers>
            </asp:UpdatePanel>           
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="ddl1" />
        </Triggers>
    </asp:UpdatePanel>

 

 

---------代码-----------

        private int _id_diyu;
        public int id_diyu
        {
            get { return ddl3.SelectedValue == "" ? 0 : int.Parse(ddl3.SelectedValue); }
            set { _id_diyu = value; }
        }