Occasional "The relationship could not be changed because one or more of the foreign-key properties is non-nullable." error

[dave0783]

I cannot re-produce this consistently, but I have gotten the following error when using this plugin:

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.

I was under the impression it had to do with my entities (See SO Question); however when disabling this plugin the issue is gone.

[bilal-fazlani]

If you could re-produce it, and find a concrete scenario when it happens, it will be possible to fix it quickly.

[jcarenton]

To reproduce the bug:

SQL Tables :

MyTable : ID int, DummyId int FK
DummyTable : ID int

MyTableEntity class :

public int ID { get; set; }
public DummyEntity Dummy { get; set; }
public int DummyId { get; set; }

Scenario :

If with a Mapper like AutoMapper you set Dummy property as NULL and you change or keep value for DummyId

• IdentityDbContext save without problem the object (of course DummyId must exist in Dummy Table)

• TrackerIdentityContext fail with message :

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.

Workaround/good practice :

Prevent editing Reference property, with AutoMapper :

.ForMember(x => x.Dummy, o => o.Ignore())

Or/And don't expose Reference property on ViewModel ...