WCF ODATA: SaveChanges() does not return modified entity

[Samuel]

I use WCF ODATA to communicate with my JavaScript client. 

When I do an update operation, the SaveChanges method is called. 

The problem is that I also use a ChangeInterceptor for setting a property value on my entity 
before saving to DB.

Now the problem is that the SaveChanges method returns void. 

It would be great if it could return the actual saved entity 
instead so that the client is aware of changes made by the server.

Am I missing something and this is already possible ? Or would that be a change request ? 

Thanks

EDIT: When an new entity is inserted, it is actually returned by the server. Only updated entities are not returned.

See the response of the $batch call for an insert:

--batchresponse_7aa4983b-fa44-4254-9013-897f986679ea
Content-Type: multipart/mixed; boundary=changesetresponse_27433a38-8952-42d8-b66b-fb7a27406c90

--changesetresponse_27433a38-8952-42d8-b66b-fb7a27406c90
Content-Type: application/http
Content-Transfer-Encoding: binary

HTTP/1.1 201 Created
DataServiceVersion: 3.0;
Content-Type: application/json;odata=fullmetadata;streaming=true;charset=utf-8
Content-ID: 1
X-Content-Type-Options: nosniff
Cache-Control: no-cache
Location: http://localhost:24497/DirectDebitModelService.svc/Mandates(48)

{"odata.metadata":"http://localhost:24497/DirectDebitModelService.svc/$metadata#Mandates/@Element","odata.type":"DirectDebitModel.Mandate","odata.id":"http://localhost:24497/DirectDebitModelService.svc/Mandates(48)","odata.editLink":"Mandates(48)","[e-mail]":"Mandates(48)/OpenPositions","AccountOwnerName":"berthelots","AccountOwnerTiersId":225956,"Amendment":0,"BIC":"BCLLLULL","CreatedBy":"berthelots","[e-mail]":"Edm.DateTime","CreatedDate":"2013-09-03T10:41:08.697","CreditorType":0,"IBAN":"LU521111000011110000","Id":48,"IsSEPAMandate":false,"MandateReference":"001/257000004","MandateType":0,"NextSequenceType":0,"OldCetrelReference":null,"PlaceOfSignature":null,"PolicyNumber":"257000004","Remarks":null,"[e-mail]":"Edm.Int64","RowVersion":"6020","SignatureDate":null,"Status":1,"UpdatedBy":null,"UpdatedDate":null}
--changesetresponse_27433a38-8952-42d8-b66b-fb7a27406c90--
--batchresponse_7aa4983b-fa44-4254-9013-897f986679ea--
and the response of the $batch call for an update. Notice that the data is not returned this time:


--batchresponse_5988bacc-ea77-43e8-8fe7-f18fe30ce710
Content-Type: multipart/mixed; boundary=changesetresponse_b5c2d17b-f7cd-42a2-a56c-e8fbbdade4ae

--changesetresponse_b5c2d17b-f7cd-42a2-a56c-e8fbbdade4ae
Content-Type: application/http
Content-Transfer-Encoding: binary

HTTP/1.1 204 No Content
Content-ID: 1
X-Content-Type-Options: nosniff
Cache-Control: no-cache
DataServiceVersion: 1.0;


--changesetresponse_b5c2d17b-f7cd-42a2-a56c-e8fbbdade4ae--
--batchresponse_5988bacc-ea77-43e8-8fe7-f18fe30ce710--

[Samuel]

Prefer Header was the answer.

see  http://msdn.microsoft.com/en-us/library/gg602811(v=vs.103).aspx. Under "Setting the Prefer Header for Change Operations",

[Dimitar Tachev]

Hello Samuel,

 
I am glad that you have found a solution to your problem.

The SaveChanges method of the OpenAccessContext does not have a return value because it is committing the current transaction which can contains a lot of insert, update and delete operations and we cannot calculate a useful return value.

In order to track the changes that are committed during your SaveChanges method calls you could take advantage of our GetChanges method. You could find a detailed description of this approach in our How to Get Changes that Will be Performed During the Next Commit documentation section.

If you need further information about the OpenAccess ORM transaction methods, you could take a look the Handling Transactions documentation article.

I hope this helps. Do not hesitate to contact us back if you need any further assistance.

Regards,
Dimitar Tachev
Telerik

[Samuel]

Well actually the solution I've found does not work with OpenAccess Data Service. It should, but for some reasons the service ignores the header and does not return the modified entity.

I'll take a look at your links.