X-45454545 X- [英] Edmx need Primary_Key?

问题描述

它的一个问题当在.net中创建Edmx时，在创建DataBase的Edmx时，只有那些表和视图被添加到谁拥有一个主键。

这个问题很容易解决，只是在列主键表或视图，但我没有得到实际的理由为什么必要？

任何人都可以解释背后的原因？

Its a problem While Creating Edmx in .net that on creating Edmx of DataBase only those Tables and views are added who had a primary key.
This problem resolved easily but just making a column primary key in Table or View but i didn't got the actual reason why it is necessary??
Can anyone please explain the reason behind it?

推荐答案

实体框架需要一个主键，才能在特定数据集中正确识别一条数据。它归结为如何在内部查找实体，并为您提供最佳性能。

Entity Framework needs a primary key to properly identify a piece of data as unique in a particular set of data. It comes down to how it looks up entities internally and giving you the best performance possible.

例如，Entity Framework的一个功能是更改跟踪，它在一系列集合中保留了添加，删除，修改和不变实体的集合，定义为 Dictionary< EntityKey，EntityEntry> 。为了能够有效地处理这些集合，它需要一个关键，以及时地对这些集合执行必要的CRUD操作，因此需要这个密钥。

For example, one of the features of Entity Framework is Change Tracking, which keeps a collection of Added, Deleted, Modified, and Unchanged entities in a series of collections defined as Dictionary<EntityKey, EntityEntry>. To be able to effectively handle those collections, it needs a key to perform the necessary CRUD operations to those collections in a timely manner, and as a result, it needs that key.

更新：

还有一个无钥匙对象的集合，但它被定义为 Dictionary< object ，EntityEntry> ，因为关键字将需要被转换（或者如果键是一个值类型，则可以取消装箱），因此可以查找这些查询的可怕性能。

There is also a collection for keyless objects as well, but it's defined as Dictionary<object, EntityEntry> which has horrible performance for lookups as the key would need to be cast (or unboxed if the key is a value type) for it to be usable.

这篇关于X-45454545 X-的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！