Why use AsNoTracking method in EF?

AsNoTracking() tells Entity Framework:

“I only want to read this data. Don’t track it for changes.”

By default, EF tracks every entity it loads so it can detect changes and generate UPDATE statements later.

Default EF behavior (Tracking ON)

var users = db.Users.ToList();

EF will:

• Keep each User in the Change Tracker
• Store original values
• Monitor property changes
• Allow SaveChanges() to persist updates

This is powerful — but not free.

What happens with AsNoTracking()

var users = db.Users
              .AsNoTracking()
              .ToList();

EF will:

• NOT track entities
• NOT store original values
• NOT detect changes

Treat results as read-only

Why use AsNoTracking()

1. Better performance

• No change-tracking overhead
• Faster query execution
• Less CPU usage

This is huge for:

• Large result sets
• Read-heavy pages
• Reports
• Public listing pages

2. Lower memory usage

Tracked entities stay in memory until:

• DbContext is disposed
• Or you manually detach them
• AsNoTracking() avoids that entirely.

3. Prevents accidental updates

If someone does:

user.Name = "Changed";
db.SaveChanges();

With AsNoTracking() → nothing happens
(no tracking = no update)

This is great for:

• Read-only screens
• API GET endpoints

4. Faster repeated queries

Tracking can slow down queries when:

• Context lives long
• Many entities already tracked

AsNoTracking() skips identity resolution and lookup cost.

When you SHOULD use AsNoTracking()

Use it when:

• You are only reading data
• No update / delete is needed

Data is used for:

• Listings
• Dashboards
• Search results
• Reports
• Public APIs

Example:

var articles = db.Articles
                 .AsNoTracking()
                 .Where(a => a.IsPublished)
                 .ToList();

When NOT to use it

Avoid AsNoTracking() if:

• You plan to update the entity
• You rely on change detection
• You use navigation fix-up

Example (don’t do this):

var user = db.Users
             .AsNoTracking()
             .First();

user.Name = "New Name";
db.SaveChanges(); // nothing saved

Quick summary

One-line answer (interview-ready)

AsNoTracking() improves performance and reduces memory usage by disabling change tracking for read-only queries in Entity Framework.