How to release tracked entities?

Question

Hopefully the following code snippet clear enough to explain the problem. _db is an instance of DbContext.

// this scenario is only for learning purpose
Author a = _db.Authors.Find(1831);
int id = a.AuthorId;
a = null;

Author stub = new Author { AuthorId = id };
_db.Remove(stub);
_db.SaveChanges();

The code above produces

'The instance of entity type 'Author' cannot be tracked because another instance with the same key value for {'AuthorId'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the conflicting key values.'

Question

How to free a from being tracked?

Answer 1

There are a variety of ways to do this, but I find this the most simple since you're trying to detach a specific entity.

_db.Entry(a).State = EntityState.Detached

As a plus it doesn't require changing any other code, including however you fetched the entity itself.

This one line makes it very clear of the intent. It also allows the following:

1. Fetch an entity, or list of entities
2. Do various types of work
3. Detach an entity

I dislike the idea of changing existing queries on a DbContext when all I want to do is detach something.