Faults and Exceptions in ASP.NET Workflows
You can model SOAP faults for a workflow Web service by using the WebServiceFaultActivity activity. The WebServiceFaultActivity activity enables you to model the occurrence of a Web service fault. This is equivalent to throwing an exception in an ASMX Web service framework method.
Unlike the ThrowActivity activity that calls an exception handler after its execution, the execution of the WebServiceFaultActivity activity does not change the course of sequential workflow execution, but it does return a SOAP exception back to the client.
The WebServiceFaultActivity activity can only be associated with a two-way request-response operation. In addition to the WebServiceFaultActivity fault, any termination of a workflow at the middle of an outstanding request-response is also thrown as a SOAP fault, with the inner exception property populated with the exception that terminated the workflow.
For more information, see the WebServiceFaultActivity class of the System.Workflow.Activities namespace in the Windows Workflow Foundation Class Library Reference.
For more information about SOAP faults and the ASMX Web service framework, see the MSDN library.