If a sender requests a response, then one will be sent regardless of whether the operation was successful or not. Therefore, whenever an operation includes a response port, you should include the World Wide Web Consortium (W3C) SOAP fault body with the port set for that message. For example, the fault body is included in this Get operation, which was included in Service Tutorial 2:

public Get(Microsoft.Dss.ServiceModel.Dssp.GetRequestType body,
         Microsoft.Ccr.Core.PortSet<ServiceTutorial2State,W3C.Soap.Fault>
         responsePort) : base(body, responsePort)
{
}

DSSP provides a set of fault codes (see Table 2-6 for a list of DSSP fault codes) that can be used to check for specific conditions. For example, when performing an insert, you could first check to see if the state item already exists using the DuplicateEntry fault code. The following code provides an example of this scenario:

if ( /* the item already exists */)
{
 insert.ResponsePort.Post(Fault.FromCodeSubcodeReason(
FaultCodes.Sender, DsspFaultCodes.DuplicateEntry));
  yield break;
}