then I wrote a code in a (Silverlight enabled WCF) to read all the data in cDetails table
[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public List<cDetail > Get_Candidates()
ttEntities1 db = new ttEntities1();
// Add more operations here and mark them with [OperationContract]
when I tried to consume this service in Silverlight client I got the error (the remote server returned an error Not Found),
I tried to consume it in widows application client and in windows 8 client I got another error
An error occurred while receiving the HTTP response to http://localhost:1552/Candidates_Service.svc. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.
the strange thing is when I remove the parent table and work without relations everything work as expected.
and the same code is working when I tried to use it to bind data directly on a web form (without using the service).
also after a lot of google search I found some articles speaking that I have to make the LasyLoadingEnabled = false
and another said it is the data size Issue so a made the LasyLoadingEnabled as false and changed the size to 2GB (there are only 4 records in the table) and the result was the same.