Entity Framework Schema Mismatch – Quick Pattern

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The Problem

Model has fields → Database missing those fields → App crashes

Detection (30 seconds)

# Check actual database
psql -h localhost -U postgres -d YOUR_DB -c "\d YOUR_TABLE"

# Check EF thinks database has
dotnet ef dbcontext script --context YourContext | grep -A 20 "CREATE TABLE.*YourTable"

Fix Pattern (5 steps)

1. Fix the Snapshot

Edit DBContextModelSnapshot.cs → Remove fields that don’t exist in real database

2. Create Migration

dotnet ef migrations add "AddMissingFields" --project YOUR_PROJECT --context YourContext

3. Review Migration

Check the generated .cs file → Ensure it adds the missing fields

4. Apply Migration

dotnet ef database update --project YOUR_PROJECT --context YourContext

5. Verify

psql -h localhost -U postgres -d YOUR_DB -c "\d YOUR_TABLE"

Prevention Rules

  1. Never manually edit database – Always use migrations
  2. Model change = Migration immediately – Don’t wait
  3. Always apply migrations after creating them
  4. Check pending migrations before deployment:
   dotnet ef migrations list --context YourContext

Production Deploy Checklist

  • [ ] Run migrations on staging first
  • [ ] Backup production database
  • [ ] Check no pending migrations: dotnet ef migrations list
  • [ ] Deploy + run migrations
  • [ ] Verify schema matches model

Golden Rule: If you change a model, immediately create and apply a migration. No exceptions.