多个添加的实体可能在实体框架中具有相同的主键

Question

I am working in a project using EF 4.0.

The Employee table has a column ReferEmployeeID which contains the employee id of the employee that is referring a new employee in the system. So Employee is a self-referencing table.

Now in the case of an employee who is not added to the system is about to add and he also refers another employee in the system, the row should be added altogether.

ActualEmployee save not called yet and then ReferEmployee.Employee = ActualEmployee

I understand the issue is that both the employees actual and refer has Employee ID set to 0, but how to come around this problem.

Answer 1

Assuming that the EmployeeID in your database table is defined as INT IDENTITY , then you could do this:

// create two new employees - one refers to the other
Employee john = new Employee { EmployeeID = -1, EmpName = "John" };
Employee peter = new Employee { EmployeeID = -2, EmpName = "Peter", ReferEmployeeID = -1 };

// add them to the EF model
ctx.AddToEmployees(john);
ctx.AddToEmployees(peter);

// save changes
ctx.SaveChanges();

So basically, define your new employees with "dummy" EmployeeID values and establish the link ( Peter references John here, by means of its "dummy" ID).

When saving this into SQL Server, the Entity Framework will handle the process of getting the real EmployeeID values (which SQL Server hands out when inserting the row) and EF will maintain that link between the two employees.