When using WCF and need to connect with the sharepoint you must do the following:
1- in web.config: Modify aspNetCompatibilityEnabled from false to true.
2- in main service you could add the below:
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
EX:
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class TestService : ITestService
{
}