Entity Framework - Code First - Multiplicity constraint violated, The role X of the relationship Y has multiplicity 1 or 0..1

Question

Using code first (EF 6), I created a 1 parent - 2 child relationship. Property is the parent object and Property Address as a child with 1 or 0..1 relationship. PropertyImage is another child with 1 to many relationship. PropertyImage works fine but the PropertyAddress throws error if I try to eager load .

Actual Error -

Multiplicity constraint violated. The role 'PropertyAddress_Property_Source' of the relationship 'MyAssetTracker.DataLayer.Models.PropertyAddress_Property' has multiplicity 1 or 0..1.

    // Test Function            
GetProperty()
{
Property property;
            using (var repo = new PropertyRepository())
            {
                property = repo.AllIncluding(a=>a.Images, a=>a.Address).FirstOrDefault(a => a.Id == testpropertyid);
            }
}


//Property Repository
public class PropertyRepository : IPropertyRepository
{


        public IQueryable<Property> AllIncluding(params Expression<Func<Property, object>>[] includeProperties)
        {
            IQueryable<Property> query = context.Properties;
            foreach (var includeProperty in includeProperties) {
                query = query.Include(includeProperty);
            }
            return query;
        }
}

//Property Entity
public class Property : DomainModelAuditBase, IDomainModelState
    {
        private Address _address;
        private ICollection<Asset> _assets;
        private ICollection<PropertyImage> _images;

        public Property()
        {
            _address = new Address();
            _assets = new List<Asset>();
            _images = new List<PropertyImage>();
        }

        public Guid Id { get; set; }
        [StringLength(100), Required]
        public string Title { get; set; }
        public bool IsPrimary { get; set; }
        [StringLength(255)]
        public string Description { get; set; }

        [NotMapped]
        public State State { get; set; }

        public Guid AddressId { get; set; }
        public Guid UserId { get; set; }

        public virtual Address Address
        {
            get { return _address; }
            set { _address = value; }
        }

        public virtual ICollection<Asset> Assets
        {
            get { return _assets; }
            set { _assets = value; }
        }

        public virtual User User { get; set; }

        public virtual ICollection<PropertyImage> Images
        {
            get { return _images; }
            set { _images = value; }
        }
    }

//PropertyAddress
public class Address : DomainModelAuditBase, IDomainModelState
{
    [Key,ForeignKey("Property")]
    public Guid PropertyId { get; set; }
    [StringLength(255),Required]
    public string AddressLine1 { get; set; }
    [StringLength(255)]
    public string AddressLine2 { get; set; }
    [StringLength(255)]
    public string City { get; set; }
    [StringLength(255)]
    public string StateProvince { get; set; }
    [StringLength(100)]
    public string PostalCode { get; set; }
    [StringLength(100)]
    public string Country { get; set; }

    [NotMapped]
    public State State { get; set; }

    public virtual Property Property { get; set; }

}

Answer 1

Remove_address = new Address(); from Property constructor. You could read about similar problem here

Also are you sure that you need AddressId field in Property class?