I have an entity that has one child and I need to update it, but, in the TryUpdateModel method, it does not accept an strong typed object (accepts only a FormCollection), and when I try to update it, I get the following error.

{"A relationship is being added or deleted from an AssociationSet 'FK\_\_SG\_Usuari\_\_ID\_Si\_\_534D60F1'. With cardinality constraints, a corresponding 'SG\_Usuario' must also be added or deleted."}

The problem is that I can't load in the formcollection the child property, only an id, but not the entire object.