ChangeTracker and the results of deserializing data of tree-like structures

[sergeykorobeynikov]

We are using generic entity classes for JSON deserialization and Entity Framework Core 6.

Here is an example of two related entities:

public class Vendor
{
	public int Id { get; set; }
	public string Name { get; set; }
	public ICollection<Category> Categories { get; set; }
}

public class Category
{
	public int Id { get; set; }
	public string Name { get; set; }
	public int? ParentId { get; set; }
	[ForeignKey(nameof(ParentId))]
	public Category Parent { get; set; }
}

When deserializing JSON data from a provider, there may be a situation where there will be two instances of the same object type with the same identifiers (Id).

As a result, data manipulation may result in an error:

System.InvalidOperationException: "The instance of entity type 'Category' cannot be tracked because another instance with the key value '{id: 1}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached."

At the same time, attempts to disable tracking do not lead to anything:
db.ChangeTracker.AutoDetectChangesEnabled = false;

It is possible to solve this problem by creating a separate dictionary for the data type, and using the key to "reassign" the correct instances, but this is very difficult for tree-like structures.

Is this some kind of flaw or is there a solution to this problem?

[ajcvickers]

@sergeykorobeynikov See Identity Resolution in EF Core and make sure to vote (👍) for #20124, which should make this easier.

[sergeykorobeynikov]

Like with respect! Now it is clear why references in JSON and XML are needed!