Ef Migrations

How to generate migrations

Step 1 — Build explicitly with the target provider

EF Core scans the compiled assembly for [Migration] attributes. You MUST build with EF_PROVIDER set so that only the target provider's migration files are compiled:

# For Sqlite
export EF_PROVIDER=Sqlite && dotnet build OwlNet.sln --no-incremental --no-restore

# For SqlServer
export EF_PROVIDER=SqlServer && dotnet build OwlNet.sln --no-incremental --no-restore

--no-incremental is required because MSBuild may cache a previous build that included the other provider's files.

Step 2 — Generate the migration with --no-build

Use --no-build to ensure dotnet ef uses the assembly you just built (and doesn't rebuild without the env var):

# Sqlite
export EF_PROVIDER=Sqlite && dotnet ef migrations add <MigrationName> \
  --project src/OwlNet.Infrastructure \
  --startup-project src/OwlNet.Web \
  --output-dir Persistence/Migrations/Sqlite \
  --no-build \
  -- Sqlite

# SqlServer
export EF_PROVIDER=SqlServer && dotnet ef migrations add <MigrationName> \
  --project src/OwlNet.Infrastructure \
  --startup-project src/OwlNet.Web \
  --output-dir Persistence/Migrations/SqlServer \
  --no-build \
  -- SqlServer

Step 3 — Verify the generated files

Each provider folder must contain:

• <timestamp>_<MigrationName>.cs — the migration Up/Down methods
• <timestamp>_<MigrationName>.Designer.cs — model metadata
• ApplicationDbContextModelSnapshot.cs — current model snapshot

Verify column types are correct for each provider:

• SqlServer: nvarchar(...), bit, int, datetimeoffset
• Sqlite: TEXT, INTEGER

Critical: snapshot overwrite problem

EF Core locates the ApplicationDbContextModelSnapshot.cs file on the filesystem (not just in the compiled assembly). When generating for the second provider, it may find the first provider's snapshot file and overwrite it with the second provider's model.

How to avoid this

Generate migrations for both providers using this exact sequence:

1. Clean start: remove all *.cs files from both Migrations/SqlServer/ and Migrations/Sqlite/ (keep .gitkeep).
2. Generate Sqlite first (the default provider):

   export EF_PROVIDER=Sqlite
   dotnet build OwlNet.sln --no-incremental --no-restore
   dotnet ef migrations add <Name> --project src/OwlNet.Infrastructure --startup-project src/OwlNet.Web --output-dir Persistence/Migrations/Sqlite --no-build -- Sqlite
   

   This creates the migration + snapshot in Migrations/Sqlite/.
3. Generate SqlServer second:

   export EF_PROVIDER=SqlServer
   dotnet build OwlNet.sln --no-incremental --no-restore
   dotnet ef migrations add <Name> --project src/OwlNet.Infrastructure --startup-project src/OwlNet.Web --output-dir Persistence/Migrations/SqlServer --no-build -- SqlServer
   

4. Check the Sqlite snapshot: after generating SqlServer, verify that Migrations/Sqlite/ApplicationDbContextModelSnapshot.cs still has TEXT/INTEGER types (not nvarchar). If it was overwritten, restore it from the Sqlite Designer file (copy BuildTargetModel content into BuildModel).

If the snapshot was overwritten

The snapshot content is identical to the Designer file's BuildTargetModel method, but renamed to BuildModel. You can manually recreate it:

1. Open the Designer file for the affected provider (e.g., Sqlite/<timestamp>_InitialCreate.Designer.cs)
2. Copy the class, change:
   • Class name from InitialCreate to ApplicationDbContextModelSnapshot
   • Base class from (none) to : ModelSnapshot
   • Method name from BuildTargetModel to BuildModel
   • Remove the [Migration("...")] attribute (keep [DbContext(...)])
3. Save as ApplicationDbContextModelSnapshot.cs in the correct provider folder

When to use me

Use this skill whenever you need to:

• Add a new EF Core migration after modifying entities or configurations
• Regenerate migrations from scratch
• Troubleshoot migration name collisions or snapshot corruption
• Understand the dual-provider migration architecture in OwlNet