Should we be treating objects created by the user in a query differently from the ones we materialize?

[divega]

Currently we have an implicit assumption that if a user writes to code to explicitly create instances of a mapped type, it is ok not to track it.

Creating this issue to have an opportunity to (re)discuss if this what we want, and how it plays with different features, present and future, like shadow properties and customer materialization through factory methods, etc.

[Condra963]

As @divega says it is ok not to track this kind of action for the user because, in my case i only use this in readonly scenarios. And as we see in the comment of the AsNoTracking method:
Disabling change tracking is useful for read-only scenarios because it avoids the overhead of setting up change tracking for each entity instance.

So in my case you should not treat the object created by the user in a query differently from the ones you materialize. And it's quite strange you treat it differently because i query Entity X and i want to create Entity X.
Maybe you should allow it that an Entity stays an Entity and does not become an Object when i apply AsNoTracking to my query. Then you give the user the choice what they want?

Without AsNoTracking

var test = _testsDbContext.Entities
    .GroupJoin(
        _testsDbContext.Joins,
        e => e.Name,
        t => t.Key,
        (e, t) => new { Entity = e, Joins = t })
    .SelectMany(
        group => group.Joins.DefaultIfEmpty(),
        (group, t) => new { group.Entity, JoinName = t.Value })
    .Select(group => new Entity() // Becomes an object
    {
        Id = group.Entity.Id,
        Name = group.JoinName ?? group.Entity.Name,
        EntityParentId = group.Entity.EntityParentId,
        EntityParent = group.Entity.EntityParent // Becomes a loaded property
    })
    .ToList();

With AsNoTracking

var test = _testsDbContext.Entities
    .AsNoTracking()
    .GroupJoin(
        _testsDbContext.Joins,
        e => e.Name,
        t => t.Key,
        (e, t) => new { Entity = e, Joins = t })
    .SelectMany(
        group => group.Joins.DefaultIfEmpty(),
        (group, t) => new { group.Entity, JoinName = t.Value })
    .Select(group => new Entity() // Stays an entity
    {
        Id = group.Entity.Id,
        Name = group.JoinName ?? group.Entity.Name,
        EntityParentId = group.Entity.EntityParentId,
        EntityParent = group.Entity.EntityParent // Stays a navigation property
    })
    .ToList();

[ajcvickers]

@smitpatel to cleanup.

[smitpatel]

We decided in meeting that, we will track entities in result if and only if they are created through materialization pipeline. Anything else we don't track.