EF Add-Migration命令快照提供了备用方案的更改

Question

I am running a theoretically simple migration. For my up() method:

    DropIndex("dbo.tableA", "IX_index_1");
    AddColumn("dbo.tableB", "column1", c => c.Int(nullable: false));
    DropColumn("dbo.tableA", "column2");

However, upon running the migration, I receive this error in my console:

Unable to update database to match the current model because there are pending changes and automatic migration is disabled

When I run the

    Add-Migration

The 'snapshot' provides the same schema changes. What is the reason for this?? Thank You.

Answer 1

This can happen if two people create migrations at the same time and check them in independently of each other.

So say you have 3 migrations A,B,C checked into source control. Two people get them and create migrations D and E. Both D and E have a snapshot of the schema that includes changes up to C. The person who created D checks in and then the person who created E gets a latest. EF will think the model is out of sync because the snapshot in E does not include D. When you add the migration, it calculates all the changes from AE including D and sees there is nothing new to do so there is nothing in the migration.

The snapshot is stored in a resx file under the migration. If you open it in the xml editor you will see the snapshot in there.

The way to fix this would be to keep the empty migration since it doesn't do any harm, or the person who did E could delete and recreate their migration so that it's snapshot includes the changes from D.

Hope that helps!

Answer 2

I wanted to add what I and my team ultimately ended up choosing.

Although I selected MikeS's answer as the chosen answer, another solution we found was to roll back to the last stable migration before the branches began interfering with one another, delete the newer migrations, and then consolidating the problematic migrations.

The Add-Migration command automatically picked up on the needed schema changes, then we added our logic for transferring records.