在Entity Framework数据库迁移期间应如何运行自定义代码？

Question

I have a very simple Entity Framework 5 DbMigration that is adding a new boolean column to an existing table with thousands of records in it. I want the initial value of that column for each existing row to be set based on the value in two other columns in the same table. This should only affect existing records, therefore should only be run when the migration is performed and never run again.

This is basically the logic that needs to be executed:

var users = (from u in context.Users select u).ToList();
users.ForEach(u =>
{
    u.MyNewBoolColumn = (u.Column1 != null && u.Column2 == "some-value");
    context.Users.AddOrUpdate(u);
});

There are two options I can think of, but I don't like either of them:

1. Create two separate migrations, since the column won't exist until after the first one is completed. This seems sloppy and I'm also not sure how to get the database context in the second migration to actually perform the update.
2. Run code in a DbMigrationsConfiguration implementation. However, this code would run every single time and I won't be able to tell if it has already run and shouldn't update records.

Is there another, better option?

Answer 1

A migration represents a change in the schema , therefor you can't use AddOrUpdate() stuff inside a migration. But you can, and this is what I would suggest you, run plain SQL code using the Sql() method.