在EF Code First迁移中使用自定义逻辑 [英] Use custom logic in EF Code First migration

问题描述

我有一个包含一定数量数据的现有数据库（即DB不为空）。现在，我决定加密一些敏感数据。我有一列 TemplateBlocks：string 。我要用新列 TemplateBlocksEnc替换它：byte [] ，并且我确实正确地更改了代码优先模型。然后我产生了迁移并...卡住了！

I have an existing Database with a some amount of data (i.e. DB is not empty). Now I made a decision to encrypt some sensitive data. I have a column TemplateBlocks : string. I'm going to replace it with new column TemplateBlocksEnc : byte[] and I did properly changed my Code First model. Then I generated migration and ... stuck!

public partial class EncryptTemplateBlocks : DbMigration
{
    public override void Up()
    {
        AddColumn("dbo.Devices", "TemplateBlocksEnc", c => c.Binary(nullable: true));

        // TODO: read TemplateBlocks data, encrypt, save to new column

        AlterColumn("dbo.Devices", "TemplateBlocksEnc", c => c.Binary(nullable: false));
        DropColumn("dbo.Devices", "TemplateBlocks");
    }

    public override void Down() { /* ... */ }
}

当然，我不打算丢失任何现有数据，我需要从旧列中读取所有数据，对其进行加密，存储到新创建的列中，然后我才能删除旧数据柱。

Of course, I do not plan to lose any existing data, I need to read all data from old column, encrypt it, store to newly created column and only then I can drop old column.

有可能吗？我想我需要某种方式来获取当前的连接/事务，但是我不知道如何进行。

Is it possible? I guess that I need somehow to get the current connection/transaction, but I have no idea how to make it.

推荐答案

您可以使用 Sql 和transact-sql：

you can use Sql and transact-sql:

public partial class EncryptTemplateBlocks : DbMigration {
public override void Up()
{
    AddColumn("dbo.Devices", "TemplateBlocksEnc", c => c.Binary(nullable: true));

    // TODO: read TemplateBlocks data, encrypt, save to new column
    Sql("UPDATE dbo.Devices SET TemplateBlocksEnc = ufn_Func(TemplateBlocks) WHERE TemplateBlocksEnc IS NULL");

    AlterColumn("dbo.Devices", "TemplateBlocksEnc", c => c.Binary(nullable: false));
    DropColumn("dbo.Devices", "TemplateBlocks");
}

public override void Down() { /* ... */ }
}

您还可以创建Transact-sql版本的加密或使用sql标准加密。

you also have the create a Transact-sql version of the encryption or use sql standard encryption.

ufn可以创建调用n Sql 。

ufn can be created with n Sql call.

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