Question

I am trying to get the total comments for an entity yet I am getting back incorrect results.

How would I get a Task and its comments counts (eagerly loaded)

        var tasks = _session.QueryOver<Task>(() => taskAlias)
                                 .Where(x => x.OrganizationID == null)
                                 .Fetch(x => x.AssignedUser).Eager
                                 .Fetch(x => x.Owner).Eager
                                 .Fetch(x => x.Comments).Eager
                                 .List();

This returns:

Task.ID 1 Comments 3
Task.ID 1 Comments 3
Task.ID 1 Comments 3

Task.ID 2 Comments 2
Task.ID 2 Comments 2

Task.ID 3 Comments 1

I want:

Task.ID 1 Comments 3

Task.ID 2 Comments 2

Task.ID 3 Comments 1

My fluent mappings are:

HasMany(x => x.Comments).Table("tComments").ForeignKeyConstraintName("fT_Task_ID").KeyColumn("fC_Resource_ID").Where("fC_Type = 'Task'").ReadOnly();

Answer 1

If I understand your issue correctly, the problem is that your getting the correct data back, it’s just duplicating at the root level. If this is the case, change your query to:

var tasks = _session.QueryOver<Task>(() => taskAlias)
                                 .Where(x => x.OrganizationID == null)
                                 .Fetch(x => x.AssignedUser).Eager
                                 .Fetch(x => x.Owner).Eager
                                 .Fetch(x => x.Comments).Eager
                                 .TransformUsing(new DistinctRootEntityResultTransformer())
                                 .List();

When you have an entity and it contains a collection of entities and you tell NHibernate to fetch the collections eagerly the SQL that is generated will essentially return as:

TASK 1 - COMMENTS 1A
TASK 1 - COMMENTS 1B
TASK 1 - COMMENTS 1C
TASK 2 - COMMENTS 2A
TASK 2 - COMMENTS 2B
...

The DistinctRootEntityResultTransformer is what we use to tell NHibernate that the root element should be unique. As your original code didn’t have the transformer your root elements are duplicated.