是否可以使用实体框架并将对象关系保留在代码中以及数据库之外

Question

I'm having a hard time just defining my situation so please be patient. Either I have a situation that no one blogs about, or I've created a problem in my mind by lack of understanding the concepts.

I have a database which is something of a mess and the DB owner wants to keep it that way. By mess I mean it is not normalized and no relationships defined although they do exist...

I want to use EF, and I want to optimize my code by reducing database calls.

As a simplified example I have two tables with no relationships set like so:

Table: Human HumanId, HumanName, FavoriteFoodId, LeastFavoriteFoodId, LastFoodEatenId

Table: Food FoodId, FoodName, FoodProperty1, FoodProperty2

I want to write a single EF database call that will return a human and a full object for each related food item.

First, is it possible to do this?

Second, how?

Boring background information: A super sql developer has written a query that returns 21 tables in 20 milliseconds which contain a total of 1401 columns. This is being turned into an xml document for our front end developer to bind to. I want to change our technique to use objects and thus reduce the amount of hand coding and mapping from fields to xml (not to mention the handling of nulls vs empty strings etc) and create a type safe compile time environment. Unfortunately we are not allowed to change the database or add relationships...

Answer 1

If I understand you correct, it's better for you to use Entity Framework Code First Approach :

1. You can define your objects (entities) Human and Food
2. Make relations between them in code even if they don't have foreign keys in DB
3. Query them usinq linq-to-sql

And yes, you can select all related information in one call.

Answer 2

You can define the relationships in the code with Entity Framework using Fluent API . In your case you might be able to define your entities manually, or use a tool to reverse engineer your EF model from an existing database. There is some support for this built in to Visual Studio, and there are VS extensions like EF Power Tools that offer this capability.

As for making a single call to the database with EF, you would probably need to create a stored procedure or a view that returns all of the information you need. Using the standard setup with lazy-loading enabled, EF will make calls to the database and populate the data as needed.