database-migration

name	database-migration
description	Create and manage EF Core database migrations safely. Use when: adding a migration, modifying schema, changing entity properties, adding indexes, updating database structure.
argument-hint	Migration description (e.g., AddCustomerTable)

Database Migration

Safely create and manage EF Core migrations with multi-database awareness.

When to Use

• Adding new tables or entities
• Modifying entity properties (columns)
• Adding indexes or constraints
• Changing relationships

Procedure

1. Pre-flight Checks

1. Verify the entity/mapping changes are complete in src/Data/Mappings/
2. Ensure DbSet<T> is registered in ApplicationDbContext
3. Check that no pending migrations exist: dotnet ef migrations list --project src/Data --startup-project src/Api

2. Create Migration

4. Generate migration:

dotnet ef migrations add {MigrationName} --project src/Data --startup-project src/Api

3. Review Migration

5. Open the generated migration in src/Data/Migrations/
6. Verify the Up() method creates the expected schema
7. Verify the Down() method properly reverses all changes
8. Generate SQL script for review:

dotnet ef migrations script --project src/Data --startup-project src/Api

4. Validate

9. Apply migration to development database:

dotnet ef database update --project src/Data --startup-project src/Api

10. Test rollback:

dotnet ef database update {PreviousMigration} --project src/Data --startup-project src/Api

Safety Rules

• Never use migrationBuilder.Sql() with user input
• Always provide reversible Down() methods
• Never drop columns and remove code in the same release
• Test migration against all supported database providers
• Use HasMaxLength() on all string properties