1     [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
 2     [System.ComponentModel.ToolboxItem(false)]
 3     // 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。
 4     [System.Web.Script.Services.ScriptService]
 5     public class ClientUtils : System.Web.Services.WebService
 6     {
 7         [WebMethod(EnableSession = true)]
 8         public void GetMSg()
 9         {
10             //do something
11         }
12     }
13 
14     public class CalculateCallback : IOMSServiceCallback
15     {
16         public void GetMsgResult()
17         {
18             string a = "2";
19         }
20     }

服务端：
1         public void GetMsgDialog()
2         {
3             ICallback callback = OperationContext.Current.GetCallbackChannel<ICallback>();
4             callback.GetMsgResult();
5         }