FLEX：如何从AS3外部类文件引用MXML类？

<![CDATA[]]>

 <?xml version="1.0" encoding="utf-8"?>
    <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
                   xmlns:s="library://ns.adobe.com/flex/spark" 
                   xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="800" minHeight="600" width="800" visible="true">
        <fx:Style source="Main.css"/>
        <fx:Declarations>
            <!-- Place non-visual elements (e.g., services, value objects) here -->
        </fx:Declarations>
        <fx:Script>
            <![CDATA[
                private var menuController:CMenuController= new CMenuController();
            ]]>
        </fx:Script>    
        <s:List x="598.35" y="100.55" width="178" height="324" id="ListBox">
            <s:layout>
                <s:VerticalLayout/>
            </s:layout>
        </s:List> 
</s:Application>