实体框架数据库第一如何改变实体，使他们从一个基类派生 [英] Entity Framework Database first How to alter entities to make them derive from a base class

问题描述

我有一个数据库已经完全在他们的数据表。我所看到的是，所有的表有5列是共同的：

I have a database already full of tables with data in them. What i have seen is that all tables have 5 columns in common:

• 的Id-长，键
• 请将isDeleted，有点
• DateDeleted，SMALLDATETIME
• LASTUPDATED，SMALLDATETIME
• LastUpdatedUser，为nvarchar

现在，也有基于那些目前正在到处复制字段做了一些常用的操作。

Now, there are some common operations that are done based on those fields which currently are replicated everywhere

我要的是建立一个只包含这些常用的属性做了他们一个基类和方法，并尽一切其他实体源于此。

What i want is to create a base class containing just these common attributes and the methods done to them and make every other entity derive from this.

我不需要或想拥有数据库本身在此基础上的实体，这只是我想帮助编码的部分。

I dont need or want to have this base entity on the database per se, this is just something i want to help the coding part.

问题是，这是数据库首先，​​我不能改变数据库，因此所有我有工作，是POCO类和EDMX。

The issue is this is Database first, i cannot alter the database so all i have to work with are the POCO classes and the EDMX.

我怎样才能做到这一点？

How can i achieve this?

推荐答案

您在找什么类似于TPH的东西（的 http://msdn.microsoft.com/en-us/data/jj618292.aspx ）

What you are looking for is something similar to TPH (http://msdn.microsoft.com/en-us/data/jj618292.aspx)

我不认为这会为你工作，但是当你有多个现有的表。

I don't think this will work for you however, as you have multiple existing tables.

其中一个可能的解决方案之一是：

One of the possible solutions is:

1. 创建名为BaseModel一个基类（或类似的东西）
2. 在添加这些属性为文摘迫使他们重写
3. 创建在基类中的方法来填充这些字段，或创建一个帮助这需要BaseModel，请将isDeleted，LASTUPDATED，LastUpdatedUser作为参数，并更新模型。
4. 扩展了的模式的.TT文件生成的部分类，并从BaseModel类继承。

1. Create a base class called "BaseModel" (or something like that)
2. Add those properties as abstracts to force them to be overridden
3. Create a method in that base class to populate those fields, or create a helper which takes BaseModel, IsDeleted,LastUpdated, LastUpdatedUser as a parameter and update the model.
4. Extend the partial classes generated by the model.tt file and inherit from the BaseModel class.

谢谢， 戴夫

这篇关于实体框架数据库第一如何改变实体，使他们从一个基类派生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！