[C#] 여러 IEntityChangeTracker 인스턴스에서 엔티티 오브젝트를 참조 할 수 없습니다. Entity Framework 4.1에서 관련 개체를 엔터티에 추가하는 동안

City와 관련된 직원 세부 정보를 저장하려고합니다. 그러나 연락처를 저장하려고 할 때마다 “ADO.Net Entity Framework IEntityChangeTracker의 여러 인스턴스에서 엔터티 개체를 참조 할 수 없습니다” 라는 예외가 발생 합니다.

나는 많은 게시물을 읽었지만 여전히해야 할 일에 대한 정확한 아이디어를 얻지 못했습니다 … 저장 버튼 클릭 코드는 다음과 같습니다.

protected void Button1_Click(object sender, EventArgs e)
    {
        EmployeeService es = new EmployeeService();
        CityService cs = new CityService();

        DateTime dt = new DateTime(2008, 12, 12);
        Payroll.Entities.Employee e1 = new Payroll.Entities.Employee();

        Payroll.Entities.City city1 = cs.SelectCity(Convert.ToInt64(cmbCity.SelectedItem.Value));

        e1.Name = "Archana";
        e1.Title = "aaaa";
        e1.BirthDate = dt;
        e1.Gender = "F";
        e1.HireDate = dt;
        e1.MaritalStatus = "M";
        e1.City = city1;

        es.AddEmpoyee(e1,city1);
    }

및 직원 서비스 코드

public string AddEmpoyee(Payroll.Entities.Employee e1, Payroll.Entities.City c1)
        {
            Payroll_DAO1 payrollDAO = new Payroll_DAO1();
            payrollDAO.AddToEmployee(e1);  //Here I am getting Error..
            payrollDAO.SaveChanges();
            return "SUCCESS";
        }

답변

EmployeeService es = new EmployeeService();
CityService cs = new CityService();

Payroll.Entities.City city1 = cs.SelectCity(...);

EmployeeService es = new EmployeeService(context);
CityService cs = new CityService(context); // same context instance

var contextOne = new EntityContext();
var contextTwo = new EntityContext();

var user = contextOne.Users.FirstOrDefault();

var group = new Group();
group.User = user;

contextTwo.Groups.Add(group);
contextTwo.SaveChanges();

var context = new EntityContext();

var user = context.Users.FirstOrDefault();

var group = new Group();
group.User = user; // Be careful when you set entity properties. 
// Be sure that all objects came from the same context

context.Groups.Add(group);
context.SaveChanges();

public class Employee{
    ...
    public int? CityId; //The ? is for allow City nullable
    public virtual City City;
}

e1.CityId=city1.ID;

Payroll.Entities.City city1;
using (CityService cs = new CityService())
{
  city1 = cs.SelectCity(Convert.ToInt64(cmbCity.SelectedItem.Value));
}

public sealed class MyModelDbContextSingleton
{
  private static readonly MyModelDbContext instance = new MyModelDbContext();

  static MyModelDbContextSingleton() { }

  private MyModelDbContextSingleton() { }

  public static MyModelDbContext Instance
  {
    get
    {
      return instance;
    }
  }
}  

public class ProjectRepository : IProjectRepository
{
  MyModelDbContext context = MyModelDbContextSingleton.Instance;
  [...]