Advice on exception handling in webservice - asp.net

Question

I need some advice on a good exception handling strategy in my webservice.
My web service methods are doing the standard CRUD operations against an Oracle database. Therefore, I have some methods that select data and return a dataset and others that do either an insert/update/ or delete and don't return anything.
Initially, I had all my code in each webservice method in a try-catch-finally catching an Oracle exception. I read some articles on the web that says this is not good and I should only surround something in try-catch if there is a potential for an exception. Now I am thinking that maybe it would be best if I put only my Insert/Update/Delete methods in try-catch-finally blocks.
So my questions are:
Should I put all my methods in try-catch-finally? They all interact with Oracle and could potentially cause an exception. Or should I only do this for the Insert/Update and Delete methods?
I don't really have any requirements on what they want to happen when an exception does occur. I am just going on common sense. I know that they definitely don't want the app to end. I am planning on logging the exception in some manner and re-throwing it to the client. I am doing this when there is an Oracle Exception.

Answer 1

Basically you need to do try-catch on every WebMethod. Since the event won't bubble up, I think there is no other better way.
However, you can use the trick in this post to make your life easier.
The way he does is creating a utility method like this and invoke that method by passing it a delegate to your web method logic.
private T Execute<T>(Func<T> body)
{
//wrap everything in common try/catch
try
{
return body();
}
catch (SoapException)
{
//rethrow any pre-generated SOAP faults
throw;
}
catch (ValidationException ex)
{
//validation error caused by client
ClientError innerError = new ClientError();
//TODO: populate client error as needed
//throw SOAP fault
throw this.GenerateSoapException(
"An error occurred while validating the client request.",
SoapException.ClientFaultCode,
innerError);
}
catch (Exception ex)
{
//everything else is treated as an error caused by server
ServerError innerError = new ServerError();
//TODO: populate server error as needed
//TODO: log error
//throw SOAP fault
throw this.GenerateSoapException(
"An unexpected error occurred on the server.",
SoapException.ServerFaultCode,
innerError);
}
}

Answer 2

I assume you are using ASP.NET WebMethods. My advice is that you always catch exceptions on the service layer, write a log and throw a SoapException. Basically you can try-catch on each service method (WebMethod). If you fail to do so, you would be exposing exception details to the client calling the service and that could be a potential security issue.