ASP.NET（C＃）Web服务中的异常处理

I was looking for a way to transfer the exception message in web services of my asp.net application to the ajax error callback function. All I could find was catching an exception thrown from web service into a C# code but i am calling my service from ajax code and not a C# code. I want something more than the HTTP status codes returned.I was looking for a way to transfer the excepti