当从列表中选择一个元素时，我希望填充其他列表

Question

我正在编写一个网络项目，我希望当从顶部下拉列表中选择一个元素时填充底部列表，我该怎么做？我需要在方法中执行此操作。

 <div>
                        <div class="control-group">
                            <label class="control-label">
                                asd</label>
                            <div class="controls">
                                <asp:ObjectDataSource ID="odsB" runat="server" SelectMethod="Liste"
                                   ></asp:ObjectDataSource>
                                <asp:DropDownList ID="ddlB" CssClass="chzn-select" runat="server" DataSourceID="odsB" OnSelectedIndexChanged="ListeleB" 
                                    DataTextField="Name" DataValueField="Id">
                                </asp:DropDownList>
                            </div>
                        </div>
                    </div>
                    <div>
                        <div class="control-group">
                            <label class="control-label">
                                dsa</label>
                            <div class="controls">
                                <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" DataSourceID="deneme" DataTextField="Ad" DataValueField="id" OnSelectedIndexChanged="Asd"></asp:DropDownList>

                                <asp:ObjectDataSource ID="odsN" runat="server" SelectMethod="ListeleN"
                                   "></asp:ObjectDataSource>
                                <asp:DropDownList ID="DropDownList1" CssClass="chzn-select" runat="server" DataSourceID="odsN"
                                    DataTextField="Name" DataValueField="Id">
                                </asp:DropDownList>
                            </div>
                        </div>
                    </div>

我的代码在这里。提前致谢。

public List<BirimDTO> ListeleB()
    {
        var cache = new SystemCacheManager();
        List<ORT_Organizasyon> lst = cache.Get<List<ORT_Organizasyon>>(SYSCACHE_B);
        //lst2.Add(new BirimDTO { BirimId = 0, BirimAdi = "Seçiniz..." });

        if (lst == null)
        {
            using (TVKEntities ctx = GetContext())
            {
                lst = ctx.ORT_O.Where(p => p.OTipId == 3).ToList();
                cache.Put(SYSCACHE_B, lst);
            }
        }

        return lst.OrderBy(p => p.BId).ToList();
    }