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

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?