<form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <asp:CheckBoxList ID="CheckBoxList3" runat="server" AutoPostBack="True" OnSelectedIndexChanged="CheckBoxList3_SelectedIndexChanged">
                <asp:ListItem>耳机</asp:ListItem>
                <asp:ListItem>充电器</asp:ListItem>
                <asp:ListItem>电池</asp:ListItem>
                <asp:ListItem>无</asp:ListItem>
            </asp:CheckBoxList>
        </ContentTemplate>
    </asp:UpdatePanel>
    </form>