How Does .AsNoTracking() Affect Entity Updates When Using Different Context Instances?

Entity Framework Core's .AsNoTracking(): Performance vs. Tracking

Entity Framework Core (EF Core) offers .AsNoTracking() to boost performance by avoiding change tracking for retrieved entities. This article examines how using .AsNoTracking() affects updating entities when different context instances are involved.

Understanding Change Tracking in EF Core

EF Core typically tracks entities retrieved from the database, monitoring changes for efficient updates. .AsNoTracking() disables this, improving performance when modifications aren't anticipated.

Scenario: Retrieving and Updating with Separate Contexts

Our scenario involves retrieving an entity (e.g., a user) using .AsNoTracking() and subsequently updating it using a different EF Core context.

The Effect of .AsNoTracking()

When .AsNoTracking() is used, the retrieved entity becomes detached from the context. Attempting to update this entity with a new context won't automatically trigger an update; the context won't recognize it as an existing record. You must manually attach the modified entity to the new context and explicitly set its state to EntityState.Modified to indicate an update is needed.

Omitting .AsNoTracking()

Conversely, if .AsNoTracking() is omitted, EF Core tracks the retrieved entity. Updating this entity with a different context will be automatically handled by EF Core, eliminating the need for manual attachment and state setting.

Choosing the Right Approach

Using .AsNoTracking() improves performance if you're certain the entity won't be modified. However, if updates are expected, omitting .AsNoTracking() simplifies the update process, as EF Core handles the tracking automatically. The choice depends on your specific needs and whether the performance gains outweigh the added complexity of manual update handling.

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