When working with a fast-evolving project changes happen rapidly not only to the project’s code but also to the database schema. It happens especially when working on a micro-service from the start when its purpose shifts.

How EF Core 5 migrations work

In Entity Framework Core 5 migrations we are adding a migration as a delta changes between our DbContext class and existing [DbContext name]ModelSnapshot. When generating new migration a CLI Tool will generate only the differences between those two and put them in two methods: Up and Down. In the first one, there will be a change to apply the migration and in the second one, to remove the migration.

After the migration is applied, its name is noted in the __EFMigrationsHistory table.

Merging multiple migrations

Let’s say that after changing a schema multiple times in the early stages our project is now stable. We have a bunch of migrations that could be merged into one, that would create a model once, without many small updates.

When we can remove everything

The easiest way to merge all migrations would be removing everything! What I mean is:

• remove Migrations directory with all migrations
• clear __EFMigrationHistory table
• remove all tables and other database objects that were added via migrations
• create new migration with all changes

This is a drastic way of merging migrations because we will lose all the data. However, it’s super simple and it might work in some cases.

When we need to preserve data

This means that we cannot remove all already created database objects, but we can merge migration files in our code. Let’s see how that can be done.

1. Delete all migration scripts from Migrations folder
2. Add a new migration with command dotnet ef migrations add MergedMigration
3. Copy the entire file and clear both Up and Down methods
4. Update the database and apply MergedMigration migration with command dotnet ef database update
5. After that, replace the content of the MergedMigration file with earlier generated code

#asp.net core for .net 5 & ef core 5 #ef core 5 #ef core migrations #primehotel