EF：Migrations.Configuration与DropCreateDatabaseAlways的种子的种子？ [英] EF: Seed of Migrations.Configuration vs Seed of DropCreateDatabaseAlways?

问题描述

我的问题原来是： DropCreateDatabaseIfModelChanges无法更新数据库？

但是我改变了它，因为这两种方法的作用更加模糊对于我
。

But I changed it because the role of these two methods is more ambiguous for me .

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到目前为止，我知道使用 DropCreateDatabaseIfModelChanges 将在架构更改（IfModelChanges）时重新创建数据库。这意味着我不必担心迁移，因为它将从头重新创建数据库，对吧？
我首先创建了一个类 DataInitializer 继承自 DropCreateDatabaseIfModelChanges ，并实现了种子方法与初始数据，并从 Database.SetInitializer（新的DataInitializer（））;
> Main 方法，但我仍然收到有关模型更改的错误，我应该添加迁移（因为我从实体中删除了一个属性来测试数据初始化）。
这是初始化器类：

What I know so far that using DropCreateDatabaseIfModelChanges will recreate the database whenever the schema changes (IfModelChanges). That mean that I don't have to worry about migration, since it will recreate the database from scratch anyway, right? I first created a class DataInitializer inheriting from DropCreateDatabaseIfModelChanges, and implemented the Seed method with the initial data, and called the Database.SetInitializer(new DataInitializer()); from the Main method, but I still get the error about model changing and I should add a migration (since I dropped a property from the entity to test the data initializing). this is the initializer class:

public class DataInitializer : DropCreateDatabaseIfModelChanges<BlogContext>
    {
        protected override void Seed(BlogContext context)
        {
            var blogs = new List<Blog>
            {
                new Blog {FollowersCount=456, Name="ABC", Url="abc.com" },
                new Blog {FollowersCount=789, Name="DEF", Url="def.com" },
                new Blog {FollowersCount=246, Name="GHI", Url="ghi.com" },
                new Blog {FollowersCount=135, Name="JKL", Url="jkl.com" },
                new Blog {FollowersCount=258, Name="MNO", Url="mno.com" },
            };
            blogs.ForEach(x => context.Blogs.Add(x));
        }
    }

这些是我的问题：如果迁移是启用，如果我在配置类中使用初始数据实现了Seed方法，那么将调用哪一个（并且我已经在Configuration类中已经使用了已经有数据的Seed方法）

These are my questions: Does it work if migration is enabled, and what happens if I'm implementing the Seed method in the Configuration class with initial data- which one will be called (and I have a Seed method initialized with data already in the Configuration class)

在我添加迁移后，它会抛出此错误（不管我是否调用SetInitializer）：

After I added a migration, it throws this error (whether I called SetInitializer or not):

已经是数据库中名为博客的对象。

There is already an object named 'Blogs' in the database.

推荐答案

你必须告诉网络.config文件在Model改变时使用初始化器类。在web.config文件中的entityFramework标签中添加以下代码。希望它会工作。

You have to tell the web.config file to use your initializer class whenever Model changes. Add the following code in the entityFramework tag in web.config file. Hope it will work..

<contexts>
    <context type="YourProjectName.BlogContext,YourProjectName">
      <databaseInitializer type="YourProjectName.DataInitializer , YourProjectName" />
    </context>
</contexts> 

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