I'm trying to insert a new Entity in EF:

```
public class Ad
{
    // Primary properties
    public int Kms { get; set; }

    // Navigation properties
    public virtual Model Model { get; set; }
}

```

And I receive from the View the model like this (example values):

kms = 222
Model.Id = 3

Then when I do the Add and SaveChanges of the Entity Framework, I get a NULL record inserted in the Model Table (that generated a new ID) and a record in the Ad Table with the new inserted Model Id.

Why is this happening?

Service Layer:

```
    public void CreateAd(CreateAdDto adDto)
    {
        var adDomain = Mapper.Map<CreateAdDto, Ad>(adDto);

        _adRepository.Add(adDomain);
        _adRepository.Save();
    }

```

Repository:

```
    public void Add(T entity)
    {
        _dbSet.Add(entity);
    }

   public void Save()
    {
        try
        {
            _dataContext.SaveChanges();
        }
        catch (DbEntityValidationException e)
        {
            var s = e.EntityValidationErrors.ToList();
            throw;
        }
    }

```

ViewModel:

```
public class CreateAdViewModel
{
    // Primary properties
    public string Version { get; set; }
    public int Kms { get; set; }
    public int Year { get; set; }
    public decimal Price { get; set; }

    public int Make_Id { get; set; }
    public int Model_Id { get; set; }

    // Navigation properties
    public IEnumerable<SelectListItem> MakeList { get; set; }
    public IEnumerable<SelectListItem> ModelList { get; set; }
}

```

Dto:

```
public class CreateAdDto
{
    // Primary properties
    public int Kms { get; set; }
    public int Model_Id { get; set; }
}

```

The Mapping:

```
        Mapper.CreateMap<CreateAdDto, Ad>().ForMember(dest => dest.Model, opt => opt.MapFrom(src => new Model { Id = src.Model_Id }));

```