WCF - "CommunicationException was unhandled by user code"

Question

What's the deal with CommunicationExceptions in a system using WCF? I have a client communicating with a server through WCF using SOAP - all async communication. Occasionally I get a CommunicationException thrown in my face - without seeing any reproducible pattern on why and when this happens.

However; I am able to continue running the program as this is only a first chance (?) exception. Therefore I assume I don't have to worry about this, and that it is handled behind the scene? But I'm still concerned, and it would be nice if someone could enlighten me on this. Should I try-catch for CommunicationException every place I call a function through WCF?

Answer 1

You could try something like this:

try
{
    ...
    client.Close();
}
catch (CommunicationException e)
{
    ...
    client.Abort();
}
catch (TimeoutException e)
{
    ...
    client.Abort();
}
catch (Exception e)
{
    ...
    client.Abort();
    throw;
}

Answer 2

The CommunicationException is the base type for all WCF related problems and can appear at the client in a multitude of cases:

• when your client e.g. requests a URL that's not available
• when your server is too busy and can't handle any more requests and rejects a request
• when something goes wrong on the network between client and server (connection dropped etc.)

If you have these pop up frequently, you'll need to check more closely if they're really CommunicationException or some derived type (FaultException and many more).

A FaultException would be an indication that something on the server went wrong - it will be thrown if the server got the request, but couldn't handle it properly and returned an exception or a SOAP fault.

Did you note what the message of the exception was, and whether there was any InnerException?

Marc