Snapshot

As explained in ASP.NET Core in Action, 3e

A tracking snapshot is a stored set of an entity's property values used to compare its original and current state.

A tracking snapshot stores the property values of an entity when EF Core loads it. When SaveChangesAsync runs, EF Core compares the current entity with that snapshot. section 12.4.4

The comparison determines the database update:

• Changed properties are included in the generated UPDATE statement. section 12.4.4
• Unchanged properties are ignored, avoiding unnecessary column writes. section 12.4.4
• The normal workflow reads a tracked entity, changes its properties, and calls SaveChangesAsync(). section 12.4.4

Figure 12.14 Updating an entity involves three steps: read the entity using EF Core, update the properties of the entity, and call SaveChangesAsync() on the DbContext to generate the SQL to update the correct rows in the database.

Follow the three-step update flow from reading an entity through generating SQL for the correct rows. section 12.4.4

How ASP.NET Core in Action, 3e covers it

How deep it goes

Explains snapshot creation and comparison, but defers alternative tracking mechanisms, disabling tracking, and inspection details.

Examples

Uses a tracked Recipe entity whose changed properties become part of an UPDATE statement.

What it assumes

Assumes familiarity with loading entities and calling SaveChangesAsync while explaining change comparison directly.

What you can do after

Evaluate/understand why EF Core updates selected columns instead of every entity property.

How it connects

Connects change tracking with Entity Framework Core, DbContext, SaveChangesAsync, and SQL UPDATE statements.

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Also explained in

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  PostgreSQL Mistakes and How to Avoid ThemA filesystem snapshot is a point-in-time representation of files and filesystem state that can be restored later.
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  Amazon Web Services in Action, Third Edition: An in-depth guide to AWSA data snapshot is a point-in-time copy of stored data that can be used to restore an earlier state.
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  API Design PatternsA snapshot is a point-in-time view of stored data that preserves the data state as of a particular instant.
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  Elasticsearch in Action, Second EditionA snapshot is a point-in-time backup of Elasticsearch index data and cluster state that can be restored later.
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  MongoDB 8.0 in Action, Third EditionA backup snapshot is a stored point-in-time copy of a database deployment's data for recovery.
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  100 SQL Server Mistakes and How to Avoid ThemA database snapshot is a read-only, point-in-time view of a SQL Server database that preserves pages as they existed when the snapshot was created.
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  Machine Learning Platform EngineeringA data snapshot is a persisted representation of data captured at a particular point in time.
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  Java Persistence with Spring Data and Hibernate epubA state snapshot is a stored copy of an entity's state used to detect changes made to the managed instance.
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  Akka in Action, Second EditionA snapshot is a persisted representation of a persistent actor's state at a point in its event history that accelerates recovery.

Compare how 11 books explain snapshot →

Related concepts

• resource revisionincludes · A resource revision is a distinct historical state of an API resource that can be retrieved or otherwise operated on separately from other states.
• provisioning toolused by · Software that creates and prepares infrastructure resources and manages their infrastructure-level dependencies.
• full backupkind of · A full backup is a complete copy of all selected data or system state at a particular point in time.
• backup and restoreused by · Backup and restore is the practice of preserving copies of data or system state and using them to recover it after loss, damage, or failure.
• snapshot isolationused by · Snapshot isolation is a transaction-isolation method in which each transaction reads a consistent versioned snapshot of committed data while concurrent writes are isolated from that view.

This explainer was generated by Manning's knowledge graph from the text of ASP.NET Core in Action, 3e. The section links point to the parts of the book it draws on.