Debug an Error in a Custom SharePoint Web Service

I have created a custom SharePoint web service that was deployed to, and successfully tested on, a test environment. Unfortunately, the web service has since stopped working, and I am trying to determine what the error is.

The web service now returns the following error in the SOAP response:

SOAP:server
Server was unable to process request.  Object reference not set to an instance of an object.

There have been no changes to the deployed web service, so I am assuming that a more recent deployment has altered the SharePoint configuration. My web service .asmx is deployed to the _vti_bin folder, and the assembly is deploy开发者_如何学Ced to the GAC. I can see the WSDL file being displayed when I browse to http://servername:port/_vti_bin/MyCustomWebService.asmx. The web methods in the assembly make use of logging (to the Windows Event log), but no logging is occurring when I try and access the web service, which suggests that the call is not getting as far as entering the web method.

Given the above, can anyone offer any suggestions as to debug this issue?

Thanks. MagicAndi.

Update

I have now realised that when I consume the web service from the endpoint http://servername:port/Site/_vti_bin/MyCustomWebService.asmx, it works, but when I use the endpoint http://servername:port/_vti_bin/MyCustomWebService.asmx, the web service fails as described above. I will update further when I diagnose the cause of the issue.

this is a try catch to get more infomraion on the exception. It will give you more information which will help debug your problem

try { 
// Do soap call here

} 
catch (System.Web.Protocols.SoapException soap_ex) 
{ 
  Console.WriteLine(soap_ex.Detail.OuterXML); 
} 
catch(System.Exception ex) 
{ 
  Console.WriteLine(ex.Message);         
}

The easiest option is to attach a debugger set to break on exceptions. If your infrastructure rules don't allow that, you'll probably need to add some additional logging to your code on the server. If you are lucky there may be enough information available in the soap message, but in my experience null reference exceptions usually need more information to be found easily.