GridView中两个DropDownList联动

Html:

<asp:UpdatePanel runat="server" ID="AccountUpdate" UpdateMode="Conditional"  >
                        <ContentTemplate>
                        <asp:GridView ID="gridAccount" runat="server" Width="100%" AutoGenerateColumns="False">
                            <Columns>

                                <asp:TemplateField HeaderText="选择一" ItemStyle-Width="15%">
                                    <ItemTemplate>
                                    <asp:DropDownList ID="ddlA" OnSelectedIndexChanged="ddlA_SelectedIndexChanged" AutoPostBack="true" runat="server" Width="50px">
                                    <asp:ListItem Value="">全部</asp:ListItem>
                                    <asp:ListItem Value="1">是</asp:ListItem>
                                    <asp:ListItem Value="0">否</asp:ListItem>
                                </asp:DropDownList>
                                    </ItemTemplate>
                                </asp:TemplateField>
                                <asp:TemplateField HeaderText="选择二" ItemStyle-Width="15%">
                                    <ItemTemplate>
                                    <asp:DropDownList ID="ddlB" runat="server" Width="50px">
                                    <asp:ListItem Value="">全部</asp:ListItem>
                                    <asp:ListItem Value="1">是</asp:ListItem>
                                    <asp:ListItem Value="0">否</asp:ListItem>
                                </asp:DropDownList>
                                    </ItemTemplate>
                                </asp:TemplateField>

</Columns>
                       </asp:GridView>
                        </ContentTemplate>
                        </asp:UpdatePanel>

CS:

public void ddlA_SelectedIndexChanged(object sender, EventArgs e)
        {

 DropDownList ddlA= (DropDownList)sender;//获取现在的事件触发者：

            GridViewRow gvr = (GridViewRow)ddlA.NamingContainer;//ddlA同属于在一个NamingContainer下

            DropDownList ddlB= (DropDownList)gvr.FindControl("ddlB");//找到ddlA的DropDownList

            ddlB.Enabled = false;

}