Radcombobox selectedindexchanged未在RadAjaxPanel中的javascript弹出窗口中触发

Question

我在选择第一个组合框时弹出javascript时使用了radcombobox，我想绑定另一个组合框。但是selectedindexchanged事件不起作用，选择也会刷新。

这是我的代码，

<div id="basic-modal-content">
          <telerik:RadAjaxPanel runat="server" ID="RadAjaxPanel1" LoadingPanelID="RadAjaxLoadingPanel1" EnableAJAX="true">
        <div class="basic_modal_form">
                <ul>
                    <li>
                        <label>Market:</label>
                        <div class="basic_modal_form_cnt">
                            <telerik:RadComboBox runat="server"  ID="ddlMarkets_Compose" OnSelectedIndexChanged="ddlMarkets_Compose_SelectedIndexChanged" AutoPostBack="true" Skin="MetroTouch" EnableEmbeddedSkins="true" AppendDataBoundItems="true"  EmptyMessage="Markets" Width="115" MaxHeight="300" DropDownAutoWidth="Enabled" CheckedItemsTexts="DisplayAllInInput">

                            </telerik:RadComboBox>
                        </div>
                        <label>Vendor Name:</label>
                        <div class="basic_modal_form_cnt">
                            <telerik:RadComboBox runat="server" ID="ddlVendors_Compose" OnSelectedIndexChanged="ddlVendors_Compose_SelectedIndexChanged" AutoPostBack="true" Skin="MetroTouch" EnableEmbeddedSkins="true"  AppendDataBoundItems="true"  EmptyMessage="Vendors" Width="115" MaxHeight="300" DropDownAutoWidth="Enabled" CheckedItemsTexts="DisplayAllInInput">
                                <Localization CheckAllString="All Vendors" />
                            </telerik:RadComboBox>
                        </div>
                    </li>

                </ul>
            </div>
        </telerik:RadAjaxPanel>
    </div>

请帮帮我......