清除EntityCollection，然后似乎无法在同一事务中添加到它 [英] Clear an EntityCollection and then Add to it within the same transaction doesn't seem possible

问题描述

我有2个实体：部门和雇员。 1个部门可以有很多员工。我想清除现有部门中的所有雇员，并将新雇员添加到该部门中，然后保存更改。它必须在单个事务中。

I have 2 entities a Department and an Employee. 1 Department can have many Employees. I would like to clear all the Employees from an existing Department, and also add a new Employee to that same department and then save the changes. It must be within a single transaction.

但是，当我尝试执行下面的代码时，数据库上出现键冲突错误。看来这显然不是要删除DepartmentEmployee表中的项目，然后再插入新的Employee。

However when I try execute the code below I get a key violation error on the database. It seems that the clear is not deleting the items in the DepartmentEmployee table, and then inserting the new Employee.

Employee newEmployee = GetNewEmployee();
department.Employees.Clear();
department.Employees.Add(newEmployee);
EntityContext.ApplyPropertyChanges("SetName", department);
EntityContext.SaveChanges();

任何对此的帮助将不胜感激。谢谢。

Any help with this would be greatly appreciated. Thanks.

推荐答案

我认为您无法通过一次调用 SaveChanges 。实体框架不保证任何特定的操作顺序。因此，我认为没有任何方法可以强制DELETE在插入之前出现，而无需另外调用 SaveChanges 。

I don't think you can do this in one call to SaveChanges. The Entity Framework does not guarantee any specific order of operations. So I don't think there is any way to force the DELETE to come before the INSERT without an additional call to SaveChanges.

另一方面，您可能可以在一个数据库事务中完成此操作。只需在新的 TransactionScope 内完成操作即可。

On the other hand, you probably can do it in one database transaction. Just do it inside a new TransactionScope.

尝试：

using (var t = new TransactionScope())
{
    Employee newEmployee = GetNewEmployee();
    department.Employees.Clear();
    EntityContext.SaveChanges();
    department.Employees.Add(newEmployee);
    EntityContext.ApplyPropertyChanges("SetName", department);
    EntityContext.SaveChanges();
    t.Complete();
}

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