HI team:

I encountered such a situation,that my WebDropDown ListContaner is blocked by some controls.

here is the code:

<div id="DivPopup">
        <link href="styles/StyleSheet1.css" rel="StyleSheet" type="text/css" />
        <asp:Panel ID="Panel1" runat="server" CssClass="drag" HorizontalAlign="Center"
            Wrap="False">
            规章制度</asp:Panel>
        <asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
                  <asp:FormView ID="FormView1" runat="server" CellPadding="4" CssClass="FormView1"
                    DataKeyNames="id" DataSourceID="SqlDataSource2" ForeColor="#333333" Width="659px"
                    DefaultMode="Insert" style="z-index:-1">
                    <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
                    <RowStyle BackColor="#E3EAEB" HorizontalAlign="Center" VerticalAlign="Middle" />
                    <InsertItemTemplate>

<table> 

<tr>
                                    <td class="td4" colspan="5">
                                        <ig:WebDropDown ID="WebDropDown2" runat="server"
                                            DropDownAnimationType="Linear" DropDownContainerHeight="0px"
                                            DropDownContainerMaxHeight="0px" DropDownContainerWidth="0px"
                                            EnableDropDownAsChild="False" MultipleSelectionType="Checkbox"
                                            PageSize="0" Width="200px"
                                            DataSourceID="SqlDataSource3" TextField="文件分类"
                                            EnableMultipleSelection="True" SelectedValue='<%# Bind("分类") %>'
                                            EnableClosingDropDownOnSelect="False" style="z-index: 1">
                                            <DropDownItemBinding TextField="文件分类" />
                                        </ig:WebDropDown>
                                    </td>

</tr>

<table/>
                                                      </InsertItemTemplate>                                    </asp:FormView>
                                <cc1:ModalPopupExtender ID="ShowFormView_ModalPopupExtender" runat="server" DynamicServicePath=""
                    Enabled="True" PopupControlID="DivPopup" TargetControlID="ShowFormView" BackgroundCssClass="popUpStyle"
                    Drag="True" PopupDragHandleControlID="Panel1">
                </cc1:ModalPopupExtender>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="btnClose" EventName="Click" />
                <asp:AsyncPostBackTrigger ControlID="btnEdit" EventName="Click" />
                <asp:AsyncPostBackTrigger ControlID="btnAdd" EventName="Click" />
                <asp:AsyncPostBackTrigger ControlID="btnFenleiClose" EventName="Click" />
            </Triggers>
        </asp:UpdatePanel>

<asp:Button ID="ShowFormView" runat="server" Style="display: none" />
                       
    </div>