Hi,

This is a bit difficult to describe but I will give it a go:

We have an entity called 'PadObjectEntity' which is defined as follows:

namespace Projecten.Model.Entities
{
    [TableMapping("PadObject")]
    public partial class PadObjectEntity : CitObjectEntity
    { ...

        [TableMapping("CitObject")]
    public partial class CitObjectEntity : PadRootEntity
    {
        /// <summary>
        /// Dit Id is de verbinding van deze class met het object in Control IT.
        /// </summary>
        [Field(Nullable = false)]
        [Metadata(IsImmutable = true)]
        public int CitObjectId { get; set; }

        /// <summary>
        /// Dit is de verwijzing naar de groep waaronder dit object in de hierarchie thuis hoort.
        /// </summary>
        [Field(Nullable = true), FieldMapping("FolderId")]
        public FolderEntity Folder { get; set; }
            ...

When a CollectionChanged for a certain list is invoked a series of routines is started updating lists in a hierarchy (tree like structure) to update lists for parent nodes in the tree.

At one point the routines get to the function below which is declared on the 'PadObjectEntity':

        void StatusListCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        Folder.StatussenList.HandleCollectionChanged<PadStatusEntity>(e);
    }

We get a NullReferenceException on the 'Folder' part of that call which is strange. I've looked the Entity up in the DB. It has key: 6653 which looks like this:

Id=6653, TypeId=126, CitObjectId=32100, FolderId=6443

Meaning there is a FolderId present for this CitObjectEntity. It looks as if DO did not fetch the Entity from the DB.

I've also looked the 'Folder' up in the DB and it's there:

Id=6443, TypeId=125, OpdrachtgeverId=NULL, MOSFolderId=1333, Naam=Martini, FolderId=5227

It is expected behavior for DO to fetch this Entity from the DB prior to executing the 'Folder' reference in the CitObjectEntity, right?

Regards Paul