Enter only key type (id) or class type for FK in essence, pros and cons

Question

I saw two types of objects, for example:

public class Person
{
    public int Id {get;set;}
    public string Name {get;set;}
    public Country Country {get;set;}
}

and like this:

public class Person
{
    public int Id {get;set;}
    public string Name {get;set;}
    public int CountryId {get;set;}
}

I think the second approach is easier and you get related data only if necessary;
which, in your opinion, is better?

Answer 1

It depends on what you want. If you want to get the country identifier, go to the second option. If you really want to use navigation properties and / or lazy loading, skip to the first option.

Personally, I use the Entity Framework and combine the options one and two:

public class Person
{
    public int Id {get;set;}
    public string Name {get;set;}
    public int CountryId {get;set;}
    public Country Country {get;set;}
}

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Answer 2

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Answer 3

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Answer 4

!

public List<Person> GetPersonsLivingIn(int countryId) {
  return ObjectContext.Persons.Where(x => x.CountryId == countryId).ToList();
}

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public List<Person> GetPersonsLivingIn(Country country) {
  return ObjectContext.Persons.Where(x => x.CountryId == country.CountryId).ToList();
}

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Answer 5

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Answer 6

STOP!

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int countryId = person.Country.Id;

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:

string countryName = person.Country.Name;

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, :

<many-to-one name="Country" class="Country" column="Country_ID" lazy="proxy" />

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Simply put, there is no need to map foreign keys in your domain model using NHibernate.