自动增量列不是标识列 [英] Auto increment a column that is not an identity column

问题描述

在一个项目中，我已经设置了项目和 ProjectMembers ，使得项目可以有一个之间的关系ProjectMembers和ProjectMemebers列表只能参加一个项目（见<一href=\"http://stackoverflow.com/questions/31783974/concurrency-check-on-an-icollection-during-add\">Concurrency检查的ICollection的（加时））。

In a project, I have set up a relation between Project and ProjectMembers such that a Project can have a list of ProjectMembers and ProjectMemebers can only participate in one project (see Concurrency Check on an ICollection (during add)).

我想有一个字段是自动递增，但是，它不应该是一个标识列。

I would like to have a field that is auto-incremented, however, it shouldn't be an identity column.

例如，给定一个项目，一旦我们添加一个新的ProjectMemeber，该成员将收到一些（类似身份证），使我们能够识别，只有ProjectMemeber在特定的项目。

For example, given a Project, once we add a new ProjectMemeber, that member will receive a number (like an id) that allows us to identify that ProjectMemeber only in that particular Project.

有没有办法实现这个使用EF？

Is there any way to achieve this using EF?

推荐答案

我将有三个实体 - 项目，成员，和一个用于名为 ProjectMembers 。

I would have three entities - Projects, Members, and one used as a relationship proxy called ProjectMembers.

这第三个实体只有3场 - ID 用作具有自动增量的身份，和专案编号和 MEMBERID 作为ForeignKey的关系。添加唯一约束，这样MEMBERID必须是唯一的（这在强制执行上的项目成员一比一的关系）。在 ID 将是唯一在该项目的成员。当他们完成一个项目，这种关系代理记录被删除，允许重新分配到另一个项目。

This third entity has only 3 fields - id used as the Identity with autoincrement, and ProjectId and MemberId as a ForeignKey relationship. Add a unique constraint such that MemberId must be unique (which enforces the one-to-one relationship on Members in Projects). The id will be unique to that member in that project. When they finish a project, that relationship proxy record is deleted, allowing reassignment to another project.

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