EF Core AsNoTracking Discover what you should not track all queries

Introduction

Tracking behavior controls whether to keep track or not of information about an entity instance when it is changed. If an entity is tracked, any changes detected in the entity will be persisted to the database during SaveChanges().

In the following example, the change to the customer address will be detected and persisted to the database during SaveChanges().

using (var context = new MyContext())
{
    var customer = context.Customers
        .Where(c => c.CustomerId == 2)
        .FirstOrDefault();

     customer.Address = "43 rue St. Laurent";
     context.SaveChanges();
}

No-tracking

No tracking query executes quickly because there is no need to setup change tracking information. It is useful when the results are used in a read-only scenario.

You can convert a query to a no-tracking query by using AsNoTracking() method.

AsNoTracking

The AsNoTracking() method returns a new query where the change tracker will not track any of the entities that are returned. If the entity instances are modified, this will not be detected by the change tracker, and SaveChanges() will not persist those changes to the database.

using (var context = new MyContext())
{
     var customers = context.Customers
         .AsNoTracking().ToList();
}

You can also change the default tracking behavior at the context instance level.

using (var context = new MyContext())
{
    context.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
    var customers = context.Customers.ToList();
}