Cannot insert the value NULL into column from unrelated entity - asp.net-mvc

Question

I'm getting a "Cannot insert null into column" error from an unrelated table when trying to add a new record for the "original" table.
I have the following two (relevant) entities:
public class Complex
{
[Key]
public Guid Id { get; set; }
public string Name { get; set; }
public Guid OwnerId { get; set; }
[ForeignKey("OwnerId")]
public Owner Owner { get; set; }
public Guid AddressId { get; set; }
[ForeignKey("AddressId")]
public virtual Address Address { get; set; }
public virtual ICollection<Unit> Units { get; set; }
public virtual ICollection<StaffMember> StaffMembers { get; set; }
public Complex()
{
this.Id = System.Guid.NewGuid();
this.Units = new HashSet<Unit>();
this.StaffMembers = new HashSet<StaffMember>();
}
public void AddUnit(Unit unit)
{
Units.Add(unit);
}
public void AddStaff(StaffMember staffMember)
{
StaffMembers.Add(staffMember);
}
}
and
public class Owner
{
[Key]
public Guid Id { get; set; }
public string Name { get; set; }
public Guid ContactInfoId { get; set; }
[ForeignKey("ContactInfoId")]
public ContactInfo ContactInfo { get; set; }
public ICollection<StaffMember> Employees { get; set; }
public ICollection<Complex> Complexes { get; set; }
public Owner()
{
this.Id = System.Guid.NewGuid();
this.Employees = new HashSet<StaffMember>();
this.Complexes = new HashSet<Complex>();
}
public void AddEmployee(StaffMember employee)
{
Employees.Add(employee);
}
public void AddComplex(Complex complex)
{
Complexes.Add(complex);
}
}
I'm trying to add a new owner in the following code:
if (ModelState.IsValid)
{
Owner newOwner = new Owner();
ContactInfo newContactInfo = new ContactInfo();
Address newAddress = new Address();
newAddress.Address1 = viewModel.ContactInfo.Address.Address1;
newAddress.Address2 = viewModel.ContactInfo.Address.Address2;
newAddress.City = viewModel.ContactInfo.Address.City;
newAddress.State = viewModel.ContactInfo.Address.State;
newAddress.Zip = viewModel.ContactInfo.Address.Zip;
newContactInfo.Address = newAddress;
newContactInfo.Email = viewModel.ContactInfo.Email;
newContactInfo.Phone1 = viewModel.ContactInfo.Phone1;
newContactInfo.Phone2 = viewModel.ContactInfo.Phone2;
newOwner.Name = viewModel.Name;
newOwner.ContactInfo = newContactInfo;
using (REMSDAL dal = new REMSDAL())
{
dal.Owners.Add(newOwner);
var result = await dal.SaveChangesAsync();
if (result > 0)
{
viewModel.ActionStatusMessageViewModel.StatusMessage = "Owner " + viewModel.Name + " added.";
viewModel.Name = "";
return View(viewModel);
}
}
}
...but getting this error:
Exception Details: System.Data.SqlClient.SqlException: Cannot insert the value NULL into column 'OwnerId', table 'REMS.dbo.Complexes'; column does not allow nulls. UPDATE fails.
The statement has been terminated.
How can I be getting an error regarding Complexes when I'm trying to add an Owner?