Benefits of AsNoTracking in Entity Framework Core: A Guide to Improved Performance

Entity Framework (EF) Core is a powerful Object-Relational Mapping (ORM) framework in the .NET ecosystem, simplifying database interactions for developers. It eliminates the need for most of the data-access code that developers usually need to write.

One often-overlooked method within EF Core is the AsNoTracking method, which can significantly impact performance and memory usage.

In this article, we’ll briefly explore the importance of AsNoTracking in Entity Framework Core, exploring scenarios where it shines and providing code samples for better understanding.

Understanding AsNoTracking

When EF Core retrieves entities from the database, it starts tracking those entities by default. This means that any changes to the entity are monitored and can be automatically persisted back to the database during the save operation. While this automatic change tracking is beneficial in certain scenarios, it might not be necessary for all queries, especially those that involve read-only operations. Read more on Tracking vs. No-Tracking Queries

This is where AsNoTracking comes into play. When applied to a query, it tells EF Core not to track the results, resulting in improved performance as EF Core doesn't have to manage the entities' state.

Benefits of AsNoTracking

Reduced Memory Consumption

Since entities retrieved with AsNoTracking are not tracked, EF Core doesn't allocate resources to store change tracking information. This can significantly reduce memory consumption, especially in scenarios where a large number of entities are queried.

Improved Query Performance

Without the overhead of change tracking, queries executed with AsNoTracking tend to perform faster. This is particularly noticeable in read-heavy scenarios where data is primarily queried for display purposes.

Taken from Microsoft EF Core documentation.

Basic Usage

The following example demonstrates the basic usage of AsNoTracking when querying entities:

Projection Queries

AsNoTracking is particularly useful in projection queries where only specific properties are selected:

Reference Loading

When dealing with related entities, AsNoTracking can be applied to prevent tracking of the entire object graph:

Detached Entities

Entities retrieved with AsNoTracking are considered detached. If you need to attach them for updates later, you can do so explicitly:

AttachRange(IEnumerable<Object>), AttachRange(Object[]), Attach(Object), Attach<TEntity>(TEntity) begins tracking the given entities, entity, entry or entries reachable from the given entities or entity using the Unchanged state by default.

Generally, no database interaction will be performed until SaveChanges() is called.

Remarks

“Disabling change tracking is useful for read-only scenarios because it avoids the overhead of setting up change tracking for each entity instance. You should not disable change tracking if you want to manipulate entity instances and persist those changes to the database using SaveChanges().”

While AsNoTracking offers performance benefits, it's essential to consider its implications. Entities retrieved without tracking won't automatically update in the database, so modifications must be handled explicitly.

Additionally, AsNoTracking might not be suitable for scenarios where entities are frequently updated.

In conclusion, AsNoTracking is a valuable tool in the Entity Framework Core toolkit, providing developers with the flexibility to optimize queries for read-heavy operations. By understanding when and how to apply AsNoTracking, developers can strike a balance between performance and functionality in their applications.

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