C# ObjectStateManager没有定义问题

我面临

ObjectStateManager

的问题

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});

我正在

使用
System.Data.Entity
和
System.Data.Objects
但是它没有显示
ObjectStateManager
的定义

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});

发件人：

使用此代码：

db.Entry(employeeFromDB).State = EntityState.Modified;
//db.ObjectStateManager.ChangeObjectState(employeeFromDB,System.Data.EntityState.Modified);
db.SaveChanges();

如果您的问题得到解决以帮助他人，则必须使用dbcontext对象接受答案！！