ObjectStateManager без определения проблемы

Я столкнулся с проблемой ObjectStateManager.

Я usingоба, System.Data.Entityи тем не System.Data.Objectsменее он не показывает определения ObjectStateManager.

SampleContext db = new SampleContext();
Employees employeeFromDB = db.Employees.Single(x => x.Id == employee.Id);

employeeFromDB.FullName = employee.FullName;
employeeFromDB.Gender = employee.Gender;
employeeFromDB.Age = employee.Age;
employeeFromDB.HireDate = employee.HireDate;
employeeFromDB.Salary = employee.Salary;
employeeFromDB.PersonalWebSite = employee.PersonalWebSite;

db.ObjectStateManager.ChangeObjectState(employeeFromDB, System.Data.EntityState.Modified);
db.SaveChanges();
return RedirectToAction("Details", new {Id = employee.Id});

c#,asp.net-mvc,entity-framework,

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