Ef Core

Entity Framework Core

Evaluate EF Core code or propose implementation changes; transform DbContext, entity, query, migration, and test concerns into concrete .NET guidance that avoids common correctness, performance, and security failures.

When to invoke

• "Review this Entity Framework Core code."
• "Give EF Core best practices for this DbContext."
• "Fix this EF Core migration or query pattern."
• "Avoid N+1 queries in this repository."
• "How should I test EF Core data access?"

DbContext and model design

Querying and performance

LINQ operator reminders

Prefer strongly-typed LINQ over raw SQL for normal data access. Common operators include Where, OrderBy, GroupBy, Skip, Take, and Select; use AsNoTracking() for read-only result sets.

Migrations and deployment

Change tracking, saving, and concurrency

• Use a scoped DbContext lifetime for web apps; do not share one context across concurrent requests.
• Batch related changes and avoid excessive SaveChanges() calls inside loops.
• Use transactions when multiple operations must commit or roll back together.
• Configure optimistic concurrency with rowversion/timestamp or concurrency tokens for multi-user updates.
• Choose tracking behavior intentionally: tracked for updates, no-tracking for read models, identity resolution when required.

Security and raw SQL

Testing guidance

Gotchas

• The in-memory provider is not relational: it can pass tests that fail against a real database; prefer SQLite or the production provider for integration behavior.
• Include() is not a performance fix by itself: it can trade N+1 queries for huge joined result sets; consider projection.
• IQueryable leaks boundaries: returning it from repositories or APIs lets callers change execution, filters, and performance outside the owner.
• Raw SQL still needs parameters: EF Core helpers can parameterize values, but string interpolation into SQL text can remain unsafe if misused.

Output template

## EF Core review — <context, entity, query, or migration>

**Status:** pass | improvements recommended | fix required | blocked
**Scope:** `<files or code areas reviewed>`

| Area | Finding | Severity | Recommendation |
| --- | --- | --- | --- |
| Querying | <issue or strength> | High | <specific EF Core change> |
| Migrations | <issue or strength> | Medium | <specific migration action> |

### Validation
- Build/tests/migration SQL reviewed: <command or not run>
- Remaining risk: <none or explicit gap>

Quality gate

• DbContext lifetime, configuration, and OnModelCreating mapping were considered.
• Entity keys, relationships, navigations, constraints, and owned entity types were checked when relevant.
• Queries were reviewed for tracking behavior, projection, pagination, Include(), compiled queries, and N+1 risk.
• Migrations were assessed for size, naming, SQL review, deployment safety, and seeding.
• Raw SQL, permissions, and sensitive data handling were checked for security issues.
• Testing advice distinguishes in-memory provider limitations from relational integration tests.