How to delete only certain child entities in entity framework - entity-framework

Question

I've searched and nothing I've come across works for this problem. I have child entities that all have a date completed field. When the parent entity is updated, I want to delete any child entities that don't have a value for the date completed field. Here's the code.
public int Save(ImmunizationForm form)
{
_context.Entry(form).State = EntityState.Detached;
//only clear our incomplete immunizations
var incompleteImmunizations = _context.ImmunizationFormImmunization.Where(x =>
x.ImmunizationFormId == form.Id && !x.DateCompleted.HasValue);
if (incompleteImmunizations.Any())
{
foreach (var i in incompleteImmunizations){
//_context.Entry(i).State = EntityState.Deleted;
_context.ImmunizationFormImmunization.Remove(i);
}
_context.SaveChanges(); //errors here
}
.....
}
My suspicion was that because I'm passing in an ImmunizationForm entity that has an Id value (meaning I'm not adding a new parent but updating), I would need to set the State to EntityState.Detached because further in my code I actually grab the entity to update from the database. But, that doesn't seem to help. As you can see I've tried both setting the State of the incompleteImmunization object to delete or just try to remove it. Neither are working. I keep getting the same error 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.
Parent class
public class ImmunizationForm
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public ImmunizationForm()
{
ImmunizationFormImmunizations = new HashSet<ImmunizationFormImmunization>();
}
public int Id { get; set; }
public string Name { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<ImmunizationFormImmunization> ImmunizationFormImmunizations { get; set; }
}
Child class
public class ImmunizationFormImmunization
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public ImmunizationFormImmunization()
{
}
public int Id { get; set; }
[ForeignKey("ImmunizationForm")]
public int ImmunizationFormId { get; set; }
public short ImmunizationTypeId { get; set; }
public byte? GroupId { get; set; }
public byte DocumentationRequirement { get; set; }
public DateTime? DateCompleted { get; set; }
public string RejectionReason { get; set; }
public DateTime? RejectedDate { get; set; }
[Column(TypeName = "numeric")]
public decimal? RejectedBy { get; set; }
public virtual ImmunizationForm ImmunizationForm { get; set; }
public virtual TypeImmunization TypeImmunization { get; set; }
}