efcore-patterns

Entity Framework Core Patterns

When to Use This Skill

Use this skill when:

• Setting up EF Core in a new project
• Optimizing query performance
• Managing database migrations
• Integrating EF Core with .NET Aspire
• Debugging change tracking issues
• Loading multiple navigation collections efficiently (query splitting)

Core Principles

1. NoTracking by Default - Most queries are read-only; opt-in to tracking
2. Never Edit Migrations Manually - Always use CLI commands
3. Dedicated Migration Service - Separate migration execution from application startup
4. ExecutionStrategy for Retries - Handle transient database failures
5. Explicit Updates - When NoTracking, explicitly mark entities for update

---

Pattern 1: NoTracking by Default

Configure your DbContext to disable change tracking by default. This improves performance for read-heavy workloads.

public class ApplicationDbContext : DbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
        // Disable change tracking by default for better performance on read-only queries
        // Use .AsTracking() explicitly for queries that need to track changes
        ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
    }

    public DbSet<Order> Orders => Set<Order>();
    public DbSet<Customer> Customers => Set<Customer>();
}

When NoTracking is Active

Read-only queries work normally:

// ✅ Fast read - no tracking overhead
var orders = await dbContext.Orders
    .Where(o => o.Status == OrderStatus.Pending)
    .ToListAsync();

Writes require explicit handling:

// ❌ WRONG - Entity not tracked, SaveChanges does nothing
var order = await dbContext.Orders.FirstOrDefaultAsync(o => o.Id == orderId);
order.Status = OrderStatus.Shipped;
await dbContext.SaveChangesAsync(); // Nothing happens!

// ✅ CORRECT - Explicitly mark entity for update
var order = await dbContext.Orders.FirstOrDefaultAsync(o => o.Id == orderId);
order.Status = OrderStatus.Shipped;
dbContext.Orders.Update(order); // Marks entire entity as modified
await dbContext.SaveChangesAsync();

// ✅ ALSO CORRECT - Use AsTracking() for the query
var order = await dbContext.Orders
    .AsTracking()
    .FirstOrDefaultAsync(o => o.Id == orderId);
order.Status = OrderStatus.Shipped;
await dbContext.SaveChangesAsync(); // Works!