flex .net交互

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" >
<mx:Script>
  <![CDATA[
import mx.controls.Alert;
import mx.rpc.events.FaultEvent;
import mx.rpc.events.ResultEvent;
private function onSuccess(evt:ResultEvent):void
   {
   Alert.show(evt.result.toString());
   }
]]>
</mx:Script>
<mx:WebService id="dataService" wsdl="http://localhost:4702/flex/WebService.asmx?wsdl" useProxy="false">
<mx:operation name="HelloWorld"  result="onSuccess(event)"  />
</mx:WebService>
<mx:Button x="73" y="48" label="Button" click="dataService.HelloWorld.send()"/>
</mx:Application>
====================FLEX==========
Imports System.Web
Imports System.Web.Services
Imports System.Web.Services.Protocols
'若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消对下行的注释。
<System.Web.Script.Services.ScriptService()> _
<WebService(Namespace:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Public Class WebService
    Inherits System.Web.Services.WebService
    <WebMethod()> _
    Public Function HelloWorld() As String
        Return "Hello World"
    End Function
End Class
===================.NET============