private void button1_Click(object sender, EventArgs e)
        {
            String request = "<invoke name=\"testExternalAPI\" returntype=\"xml\"><arguments><string>Sent by C#</string></arguments></invoke>";
            try
            {
                this.flashResponse_txt.Text = this.flashControl.CallFunction(request);
            }
            catch 
            {
                this.flashResponse_txt.Text = e.ToString();
            }
            
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            String swfPath =  @"M:\ECX\FLASH\bin\Desktop.swf";
            this.flashControl.LoadMovie(0, swfPath);

        }

        private void flashControl_FlashCall(object sender, AxShockwaveFlashObjects._IShockwaveFlashEvents_FlashCallEvent e)
        {
            this.flashRequest_txt.Text = e.request;
            MessageBox.Show(e.request);
            this.flashControl.SetReturnValue("<string>C# Return 的内容</string>");

        }

    <?xml version="1.0" encoding="utf-8"?>
    <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" width="800" height="600" applicationComplete="init()">
    <mx:Script>
        <![CDATA[
            //import RP.Comm;
            function init():void {
                ExternalInterface.addCallback("testExternalAPI", tst);
            }
            
            
            
            function test():void{
                lblTest.text = ExternalInterface.call("testSentCSharp", "这里可以添加传入的参数");
                return;
            }

        function tst(paramTxt:String):String {
            lblTest.text = paramTxt;
            return "这是来自Flex的Return";
        }
            
        ]]>
    </mx:Script>

        <mx:Button x="117" y="114" label="Button" click="test()"/>
        <mx:Label x="19" y="10" text="abc" id="lblTest"/>
    </mx:Application>