Migrate

/migrate

What

The single migration workflow for three change types, with EF Core schema migrations as the primary flow:

1. EF Core schema — review pending model changes, generate a descriptively named migration, review the SQL for data loss and locking risks, apply with a documented rollback path.
2. .NET version upgrade — phased TFM/SDK/package upgrade with verification at each phase.
3. NuGet updates — incremental, one-package-at-a-time updates so breakage is always attributable.

Shared principles: verify before applying, rollback plan always, test after every step, one logical change per migration.

When

• After modifying entity classes, DbContext configuration, or relationships
• "add migration", "update database", "create migration", "new table", "rename column"
• When generating SQL scripts for DBA review
• "upgrade to .NET 10", "version upgrade", ".NET upgrade"
• "upgrade nuget", "update packages", "dependency update", vulnerable package alerts

How

First, classify the request: schema change → Flow A; framework upgrade → Flow B; package update → Flow C. Then follow that flow end to end.

Flow A: EF Core Schema Migration (primary)

Step 1: Assess current state

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dotnet ef migrations list --project <InfraProject> --startup-project <ApiProject>

Check for pending migrations and uncaptured model changes.

Step 2: Review model changes

Use MCP tools instead of reading whole files:

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find_symbol(name: entity or DbSet)        -- locate the changed entity
get_type_hierarchy(typeName: entity)      -- check TPH/TPT/TPC inheritance changes
find_references(symbolName: property)     -- assess downstream query impact

Confirm the change is one logical unit. If not, split into multiple migrations — mixed migrations make rollback all-or-nothing.

Step 3: Generate migration

Name describes the change, not the entity: Add|Remove|Rename|Modify + WhatChanged.

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# GOOD
dotnet ef migrations add AddOrderShippingAddress --project <Infra> --startup-project <Api>
# BAD — names the entity, not the change
dotnet ef migrations add Order

Step 4: Review generated SQL

database update has no dry-run flag — preview by generating an idempotent script and reading it:

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dotnet ef migrations script --idempotent --project <Infra> --startup-project <Api>

Flag and report:

• DROP COLUMN / DROP TABLE — confirm data loss is intentional
• ALTER COLUMN type changes — check precision loss or truncation
• ALTER on large tables — warn about lock duration
• New non-nullable columns — need defaults for existing rows

If data must survive a rename/retype, use a multi-step migration with raw SQL:

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protected override void Up(MigrationBuilder migrationBuilder)
{
    migrationBuilder.AddColumn<string>("ContactEmail", "Customers", nullable: true);
    migrationBuilder.Sql("UPDATE \"Customers\" SET \"ContactEmail\" = \"Email\"");
    migrationBuilder.AlterColumn<string>("ContactEmail", "Customers", nullable: false);
    migrationBuilder.DropColumn("Email", "Customers");
}

Step 5: Apply and verify

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dotnet ef database update --project <Infra> --startup-project <Api>
dotnet build && dotnet test   # integration tests catch schema mismatches

Step 6: Document rollback

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dotnet ef database update <PreviousMigrationName> --project <Infra> --startup-project <Api>
dotnet ef migrations remove --project <Infra> --startup-project <Api>   # if unapplying from code

Never modify a migration that is already applied — create a new one.

Flow B: .NET Version Upgrade

1. Assess — get_project_graph to list all TFMs; flag mixed versions.
2. Pre-flight — all tests green, no pending EF migrations, dependencies checked for target-version compatibility, dedicated branch created (branch IS the rollback plan).
3. Update global.json — SDK version with "rollForward": "latestMinor".
4. Update TFMs — <TargetFramework>net10.0</TargetFramework> and <LangVersion>14</LangVersion> in .csproj or Directory.Build.props.
5. Update packages — dotnet outdated --upgrade Major --include Microsoft.*, then build and fix.
6. Adopt new features — per knowledge/dotnet-whats-new.md: TimeProvider, HybridCache, primary constructors, collection expressions.
7. Verify — dotnet build, dotnet test, dotnet format --verify-no-changes.

Flow C: NuGet Package Updates

1. Audit — dotnet list package --outdated and dotnet list package --vulnerable. Vulnerable packages are urgent: update, test, deploy.
2. Categorize — patch (batch-safe), minor (one at a time), major (one at a time, read release notes first).
3. Update incrementally — one package, then dotnet build && dotnet test before the next. Batched updates make failures unattributable.
4. Check fit — consult knowledge/package-recommendations.md before adding new packages; prefer built-in .NET alternatives. Moving off MediatR (commercial license from v13)? Follow the step-by-step guide in knowledge/mediatr-to-mediator-migration.md.
5. Rollback — git revert the package bump; never downgrade other packages to compensate.

MCP Tools Used

• find_symbol / find_references — locate entities, assess schema-change impact
• get_type_hierarchy — entity inheritance for TPH/TPT/TPC
• get_project_graph — TFM audit before version upgrades
• get_diagnostics — catch warnings after migration generation or upgrades

Example

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User: /migrate

Claude: Checking migration state...
  Last applied: 20250710_AddOrderTable
  Model changes detected: new ShippingAddress property on Order entity.

  Creating migration: AddOrderShippingAddress
  Reviewing SQL (dotnet ef migrations script --idempotent)...
  - ALTER TABLE "Orders" ADD "ShippingStreet" text NULL
  - ALTER TABLE "Orders" ADD "ShippingCity" text NULL
  No data loss. No locking risk. Safe to apply.

  Applying migration... Done. Build: green. Tests: 34/34 passed.

  Rollback (if needed):
  dotnet ef database update AddOrderTable --project src/Infrastructure --startup-project src/Api

Related

• ef-core — entity configuration, query patterns, migration internals
• /verify — full verification pipeline after migration work
• /checkpoint — commit a safe state before risky migrations