EF5 code首先：要检测是否要创建一个数据库，这样我就可以运行ALTER语句 [英] EF5 Code First: Detect if it creates a database so I can run ALTER statements

问题描述

我是新与实体框架5.我们的团队正在使用 code首先的工作流程。

I am new with Entity Framework 5. Our team is using Code First workflow.

在我开始与我的主要问题，的让我先告诉你我已经尝试的^{（所有时间的最终意见：D 的）}。

Before I'll start with my main question, let me first show you what I have tried ^{(the ultimate comment of all time :D)}.

public class MyDBContext : CDBContext
{
    public MyDBContext() : base(connString) { }

    public MyDBContext(string connStr) : base(connStr) { }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // removes some conventions
        modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
        // ........

        // model configurations which contains mappings
        modelBuilder.Configurations.Add(new AccountConfiguration());
        // ........

        // calls base OnModelCreating
        base.OnModelCreating(modelBuilder);
    }

    // list of all Entity
    public DbSet<Account> Account { get; set; }
}

MyDBContext 是继承了 CBDContext 包含重写方法并且还继承了<我已创建的类code>的DbContext 。其中一个我遇到的问题是，实体框架不处理领域的独特性。我已阅读的文章配置/映射属性，并用流利的API 类型他们的网站上，我找不到任何配置属性设置成独一无二的。

MyDBContext is the class I have created that inherits from CBDContext that contains override methods and which also inherits from DBContext. One of the problems I have encountered is that entity framework doesn't handle field uniqueness. I have already read the article on Configuring/Mapping Properties and Types with the Fluent API on their site and I can't find any configuration to set a property into unique.

所以，我为了设置领域独树一帜的手动运行创建过程中的几个ALTER SQL语句一样，

So what I did in order to set the field unique is to manually run several ALTER sql statements during creation,

using (MyDBContext _context = new MyDBContext(connString))
{
    if (_context.Database.CreateIfNotExists()) 
    {
        _context.Database.ExecuteSqlCommand("ALTER TABLE Account ADD CONSTRAINT UQ_Account_AccountNumber UNIQUE(AccountNumber)");
        _context.Database.ExecuteSqlCommand("ALTER TABLE Account ADD CONSTRAINT UQ_Account_GUID UNIQUE(GUID)");
        // .... more on this in the following lines ...
    }
}

我的问题：

1. 我是正确的，实体框架的没有任何配置或数据注解的到的设置领域独树一帜的？
2. 有没有办法在运行时发现或知道是否EF创建一个数据库或不这样我就可以移动或隐藏这一说法如果（_context.Database.CreateIfNotExists（））某处，可重写的可利用的方法？

1. Am I right that entity framework don't have any configuration or data annotations to set the field unique?
2. Is there a way to detect or know during runtime if EF creates a database or not so I can move or hide this statement if (_context.Database.CreateIfNotExists()) somewhere to an available method that can be overriden?

我真正想要的是移除如果（_context.Database.CreateIfNotExists（））从使用statemnt并把它放在别的地方或内部 MyDBContext 所以我的code看起来像这样，

What I really want is to remove if (_context.Database.CreateIfNotExists()) from the using statemnt and put it somewhere else or inside MyDBContext so my code will look like this,

using (MyDBContext _context = new MyDBContext(connString))
{
    Account _acc = new Account()
    // ...Account properties ...

    _context.Account.Add(_acc);
    _context.SaveChanges();
}

感谢。

推荐答案

如果你不使用（或无法使用），EF迁移，你可以使用自定义的初始化中所提到的这个答案。自定义初始化将创建数据库之后执行种子方法=只有一次，当数据库中不存在。如果您需要逐步开发数据库初始化本身不会帮助你（这就是迁移是）。

If you don't use (or cannot use) EF migrations you can use custom initializer as mentioned in this answer. The custom initializer will execute a Seed method after creating the database = only once when database doesn't exist. If you need to incrementally develop the database initializer itself will not help you (that is what migrations are for).

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