使用实体框架将POCO手动映射到现有的表 [英] Manually map POCO to existing Table using Entity Framework

问题描述

我有一个现有的数据库表 Movie 。现在我想写一个映射到该表的POCO Movie.cs 。我想控制映射，部分是因为我正在尝试更多地了解EF。

电影表格有3个字段：标题VARCHAR（255，），ReleaseDate DATETIME，Price MONEY 。我的DbContext派生类是什么样的？

从Java / Hibernate的背景出发，我想我将POCO中的字段映射到表中的cols ，但在EntityFramework中看起来并不直接。

我似乎只找到这两个选项：

1. Code First - >将所有内容写入C＃，然后让EntityFramework生成和运行迁移，以不断更新和种子数据库。


数据库优先 - >创建数据库，然后在VS中创建一个DB项目，并生成一个为您生成POCO的EDMX文件

对于将单个POCO映射到单个表的目标，两者似乎都过于钝。我失踪了什么我听说过流利的API，但这似乎让我回到了1.或者2。

我努力找到文档中一致的内容我正在寻找。

解决方案

你有另一个选择。您可以编写POCO类，映射类并禁用迁移（迁移还涉及您的数据库中没有的名为__MigrationHistory的元数据表）。

该类可以（使用属性映射字段，您可以使用流畅的界面）

  class Movie {
 [PrimaryKey ] 
 [MaxLength（255）
 public string Title {get; set;} 
 public datetime ReleaseDate {get; set;} 
 public float Price {get; set;} //或者你推荐的类型
} 
  

要禁用迁移和模型检查我通常将它设置在上下文类（即MyContext类）中。

  class MyContext：DbContext {
 
 static MyContext（）
 {
 System.Data.Entity.Database.SetInitializer< CloseUpContext>（null）; //这将禁用模型检查
} 
 
 public DbSet< Movie>电影{get; set;} 
 
 
} 
  

一个有趣的功能是CodeFirst从数据库。 EF从数据库开始生成POCO类。课程通常需要重构，但仍然比从头开始写课程还要好。

I have an existing database table Movie. Now I want to write a POCO Movie.cs which will map to that table. I want to have control over the mapping partially because I'm trying to learn more about EF.

The Movie table has 3 fields: Title VARCHAR(255,), ReleaseDate DATETIME, Price MONEY. What would my DbContext - derived class look like for this?

Coming from a Java/Hibernate background, I figured I would just map fields in the POCO to cols in the table, but it doesn't seem that straight forward in EntityFramework.

I only seem to find these 2 options:

1. "Code First" -> write everything in C#, then let EntityFramework generate and run migrations to constantly update and seed the DB.

2. "Database First" -> create the DB, then create a DB project in VS and generate an EDMX file which generates the POCO's for you

Both seem overly obtuse for the goal of mapping a single POCO to a single table. What am I missing? I've heard reference to "Fluent API," but that seems to lead me back to 1. or 2.

I struggled to find anything consistent in the docs that described what I was looking for.

解决方案

You have another option. You can write POCO class, map the class and disable migrations (migration involves also a metadata table called __MigrationHistory that you don't have in your database).

The class could be (using attributes to map the fields, you can use fluent interface as well)

class Movie {
    [PrimaryKey]
    [MaxLength(255)
    public string Title {get; set;}
    public datetime ReleaseDate {get; set;}
    public float Price {get; set;} // Or the type you prefere
}

For disable the migration and the model checking I usually set it in the context class (i.e. MyContext class).

class MyContext : DbContext {

    static MyContext()
    {
        System.Data.Entity.Database.SetInitializer<CloseUpContext>(null); // This disables model checking
    }

    public DbSet<Movie> Movies {get; set;}


}

An interesting feature is CodeFirst from Database. EF generates the POCO classes starting from database. Classes often need a refactoring but is still better than writing classes from scratch.

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