webservice支持跨域

<system.webServer>
    <!--解决跨域请求 by wys -->
    <httpProtocol>
      <customHeaders>
        <add name="Access-Control-Allow-Methods" value="OPTIONS,POST,GET" />
        <add name="Access-Control-Allow-Headers" value="x-requested-with,content-type" />
        <add name="Access-Control-Allow-Origin" value="*" />
      </customHeaders>
    </httpProtocol>
  </system.webServer>