Author: foyezahmedfj20@gmail.com

When working with Entity Framework Core, loading related data efficiently is just as important as writing correct queries.

EF Core provides three approaches:

• Eager Loading
• Lazy Loading
• Explicit Loading

Each has its own strengths and trade-offs.

Choosing the wrong one can lead to unnecessary database calls and poor application performance.

Let’s explore when to use each.

1. Eager Loading

Eager loading retrieves the main entity and its related data in a single query using Include().

Example:

var orders = await context.Orders
    .Include(o => o.Customer)
    .ToListAsync();

Here, both Orders and their related Customer data are loaded together.

Use Eager Loading When:

• You know you’ll need the related data.
• You want to minimize database round trips.
• You’re building APIs that return complete object graphs.

Pros

• Fewer database queries.
• Better performance in many scenarios.
• Easy to understand.

Cons

• Can retrieve unnecessary data if overused.
• Multiple Include() calls may produce complex SQL queries.

2. Lazy Loading

With lazy loading, related data isn’t loaded until it’s actually accessed.

Example:

var order = await context.Orders.FirstAsync();

var customer = order.Customer;

The second line triggers another database query.

Use Lazy Loading When:

• Related data is rarely needed.
• Simplicity is more important than maximum performance.

Pros

• Loads data only when needed.
• Cleaner code.

Cons

• Can generate many hidden database queries.
• May lead to the N+1 query problem.
• Less predictable performance.

3. Explicit Loading

Explicit loading gives you full control over when related data is retrieved.

Example:

var order = await context.Orders.FirstAsync();

await context.Entry(order)
    .Reference(o => o.Customer)
    .LoadAsync();

The related entity is loaded only when you explicitly request it.

Use Explicit Loading When:

• You only need related data in specific scenarios.
• You want predictable database access.
• You’re optimizing performance-critical code.

Pros

• Full control over database queries.
• Avoids unnecessary loading.

Cons

• Requires additional code.
• Easier to forget loading related entities.

Beware of the N+1 Query Problem

Consider this:

var orders = await context.Orders.ToListAsync();

foreach (var order in orders)
{
    Console.WriteLine(order.Customer.Name);
}

If lazy loading is enabled, EF Core may execute:

• 1 query for all orders.
• 1 additional query for each customer.

If there are 100 orders, that could result in 101 database queries.

This is known as the N+1 query problem, and it can significantly impact performance.

Which One Should You Choose?

Final Thoughts

There isn’t a single “best” loading strategy.

The right choice depends on your application’s requirements.

My general rule is:

• Prefer Eager Loading for APIs and common queries.
• Use Explicit Loading when you need fine-grained control.
• Use Lazy Loading carefully, especially in high-performance applications, to avoid hidden database queries.

Understanding these loading strategies can help you build faster, more efficient EF Core applications.