Because these two lines …
EmployeeService es = new EmployeeService(); CityService cs = new CityService();
… don’t take a parameter in the constructor, I guess that you create a context within the classes. When you load the city1
…
Payroll.Entities.City city1 = cs.SelectCity(...);
…you attach the city1
to the context in CityService
. Later you add a city1
as a reference to the new Employee
e1
and add e1
including this reference to city1
to the context in EmployeeService
. As a result you have city1
attached to two different context which is what the exception complains about.
You can fix this by creating a context outside of the service classes and injecting and using it in both services:
EmployeeService es = new EmployeeService(context); CityService cs = new CityService(context); // same context instance
Your service classes look a bit like repositories which are responsible for only a single entity type. In such a case you will always have trouble as soon as relationships between entities are involved when you use separate contexts for the services.
You can also create a single service which is responsible for a set of closely related entities, like an EmployeeCityService
(which has a single context) and delegate the whole operation in your Button1_Click
method to a method of this service.ShareFollow