用于POCO的EF中的自定义数据访问 [英] Custom Data Access in EF for POCO

问题描述

我正在编写一个WCF数据服务，旨在从预定义的标准结构中的任何数据库提取数据。

我在想使用POCO实体。我可以在EF设计器上设计我的实体，并从中生成POCO类，但是我很难理解的是如何编写数据访问层并将其注入到DBContext中。

因此，对于每个不同的数据库，我将有一个数据访问层，它将从数据库或甚至xml文件中检索数据，并将数据映射到我的POCO实体。

我不知道这是否可以实现。

POCO类将是我的标准结构，以暴露给世界。
我无法看到任何地方编写自定义sql查询从数据库中提取数据，然后在POCO类中设置数据。 POCO类不匹配任何数据库表，所以我明确地需要将数据库字段映射到POCO类，但我不知道如何使用POCO在Entity Framework中执行此操作。

我相信POCO是写入选项，但是在数据访问层和数据库映射到POCO类之间挣扎。

我看到的所有示例都谈到连接EF直接到现有的数据库。意思是EF结构必须匹配数据库的结构。我想要的是一个单一的EF / POCO结构，可以从多个数据库检索数据。这些数据库不具有相同的结构，但是我需要从这些数据库中手动检索数据，并将转换为到POCO类结构中。我不一定要一次从多个数据库获取数据，而是从单个数据库获取数据，但是要为任何数据库使用相同的模型 - 所以我想我必须为每个数据库编写一个自定义DAL，该数据库从数据库获取数据，将数据转换为POCO模型结构。

如果有人能帮助我，我真的很感激。

顺便说一下，我是EF的新手，请耐心等待。

解决方案

你是否遵循这个教程，向您展示如何从数据库中创建模型类并对其进行查询？

另外这里是一个伟大的教程，使用EF代码 - 首先，您首先构建您的POCO类，并为您生成数据库。好阅读：）。

I am currently writing a WCF data service that is meant to extract data from any database in a predefined standard structure.

I was thinking of using POCO entities. I can design my entities on EF designer and generate the POCO classes from it but the bit I struggling to understand is how to write data access layer and inject it into the DBContext.

So for each different database, I'll have a data access layer that will retrieve data from a database or even an xml file and map the data to my POCO entities.

I am not sure if this is achievable at all.

The POCO classes will be my standard structure to expose to the world. I can't see anywhere to write custom sql queries to extract data from a DB and then set the data in the POCO classes. The POCO classes do not match any of the database tables so I explicitly need to map database fields to the POCO classes but I am not sure how to do this in Entity Framework using POCO.

I believe POCO is the write option but struggling on the data access layer and mappings from database to POCO classes.

All the samples I have seen talk about connecting the EF to an existing database directly. Meaning the EF structure has to match the structure of the database. What I want is a single EF/POCO structure that can retrieve data from multiple databases. These databases do not have the same structure but I need to manually retrieve data from these databases and transform it into the POCO classes structures. I do not necessarily want to get data from multiple databases at once but from a single DB but want to use the same model for any database - So I guess I have to write a custom DAL for each database which gets the data from a DB and transform the data into the POCO model structure.

I would really appreciate if anyone could help me.

By the way I am new to EF so please be patient.

解决方案

Have you followed this tutorial which shows you how to create model classes from a DB and query against them?

Also here is a great tutorial on using EF code-first, in which you build your POCO classes first, and it generates the DB for you. Great read :).

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