有懂Ext.net的大神吗？为什么小弟我的不支持FieldContainer

有懂Ext.net的大神吗？为什么我的不支持FieldContainer？
由于项目需要，第一次使用Ext.net做，可是我的为什么不支持FieldContainer啊？代码完全是按照官方例子拷贝下来的也不行啊

<ext:FormPanel 

        runat="server" 

        Height="400"

        Width="600"

        Title="Form Panel" 

        BodyPadding="5" 

        MonitorResize="true">

        <Items>

            <ext:FieldContainer 

                runat="server" 

                FieldLabel="Text fields" 

                AnchorHorizontal="100%" 

                Layout="HBoxLayout">                                       

                <Items>

                    <ext:TextField runat="server" Width="150" Margins="0 3 0 0" />

                    <ext:TextField runat="server" Width="150" />

                </Items>

            </ext:FieldContainer>

            

            <ext:FieldContainer 

                runat="server" 

                FieldLabel="50% / 50%" 

                AnchorHorizontal="100%"

                Layout="HBoxLayout">

                <Items>

                    <ext:TextField runat="server" Flex="1" Margins="0 3 0 0" />

                    <ext:TextField runat="server" Flex="1" />

                </Items>

            </ext:FieldContainer>

            

            <ext:FieldContainer 

                runat="server" 

                FieldLabel="Fill" 

                AnchorHorizontal="100%"

                Layout="HBoxLayout">

                <Items>

                    <ext:TextField runat="server" Width="150" />

                    <ext:DisplayField runat="server" Flex="1" Html="&nbsp;" />

                    <ext:TextField runat="server" Width="150" />

                </Items>

            </ext:FieldContainer>

        </Items>

    </ext:FormPanel>

------解决方案--------------------
应该是版本问题吧