Entity Framework Inheritance relational tables

Question

I have tried several things before coming here, such as different model approach, annotation, declarations in DbContext, different fluent API usages but I can't seem to see what the issue is.

I have a YogaClass record but when I iterate over the subscriptions from a person, I have a subscription but no YogaClass (NULL) and yes I.Include(Person.Subscriptions) when querying the DB, I'm getting the subs but not the relational YogaClass/WorkShop associated with it.

In short, I have the following classes :

Subscription (base class)

public class Subscribtion
{
    [Key]
    public int SubscribtionID { get; set; }

    public Person Person { get; set; }
    public bool IsPayed { get; set; }
}

WorkshopSubscription (inherrits Subscription)

public class WorkshopSubscribtion : Subscribtion
{
    [Key] 
    public int WorkshopSubscribtionID { get; set; }
    public Workshop Workshop { get; set; }
}

YogaClassSubscription (inherrits Subscription)

public class YogaClassSubscribtion : Subscribtion
{
    [Key] 
    public int YogaClassSubscribtionID { get; set; }
    public YogaClass YogaClass { get; set; }
}

YogaClass (base class)

public class YogaClass
{
    [Key]
    public int YogaClassID { get; set; }
    public List<Subscriptions> Subscriptions { get; set; }
}

WorkShop (base class)

public class WorkShop
{
    [Key]
    public int WorkShopID { get; set; }
    public List<Subscriptions> Subscriptions { get; set; }
}

Now after I insert some records in the Seeder I have the following issue when I look into my DataBase:

Table Subscription : SubscriptionID:1 , WorkShop_WorkShopID:NULL , YogaClass_YogaClassID:NULL . (Why are they both NULL ?)

Table YogaClassSubscription : SubscriptionID:1 , YogaClassID:1 Same for workshop.

I don't get why the FK from Yoga & Workshop Subscription is NULL in Subscription table.

I have a DbSet declared in my Context and in modelBuilder fluent API method I have mapped both YogaClassSubscribtion & WorkShopSubscribtion to their own table.

public DbSet<Subscribtion> Subscribtions { get; set; }       
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<WorkshopSubscribtion>().ToTable("WorkshopSubscribtions");
    modelBuilder.Entity<YogaClassSubscribtion>().ToTable("YogaClassSubscribtions");
}

Why is it easier to post screenshots than to copy past code? — user4189129
– user4189129, Commented Dec 9, 2016 at 14:17
i find it not readable at all when pasting code , yes if i got the code inserting part working completely it would but i don't , i replace 'enter code here' with the code but its only rendereing partial code so yes i find this more easier. However if you want i can paste the code. — Dimitri
– Dimitri, Commented Dec 9, 2016 at 14:21
Like you see i can't get all code to be shown correctly and i am doing it the exact same way ... Again sorry but idk how that comes. — Dimitri
– Dimitri, Commented Dec 9, 2016 at 14:33
I have tryed removing DbSet<Subscription> and instead add the classes that are inherriting from it but i got the same result , i tryed with setting the relations with the Fluent API and with Annotations but still same result , what am i overseeing here ... ? Kind regards — Dimitri
– Dimitri, Commented Dec 9, 2016 at 15:42

Diana · Accepted Answer · 2016-12-09 17:36:13Z

1

I think your problem comes from using the base class Subscription as the type of your generic lists Subscriptions. You should use the specific derived classes YogaClassSubscription and WorkShopSubscription:

public class YogaClass
{
    [Key]
    public int YogaClassID { get; set; }
    public virtual List<YogaClassSubscription> Subscriptions { get; set; }
}

public class WorkShop
{
    [Key]
    public int WorkShopID { get; set; }
    public virtual List<WorkShopSubscription> Subscriptions { get; set; }
}

This way EF knows about the relationship between WorkShops and WorkShopSubscriptions, and between YogaClasses and YogaClassSubscriptions.

Another thing that seems wrong: redefining the ID property and the Key annotations in your derived classes. You only need to define the ID in the base class. Remove those properties and their annotations. EF will create a foreign key with a one-to-one relationship between your base class table and the derived classes tables.

public class WorkshopSubscription : Subscription
{
    public virtual Workshop Workshop { get; set; }
}

public class YogaClassSubscription : Subscription
{
    public virtual YogaClass YogaClass { get; set; }
}

An advice: define your navigation properties as virtual, in order to allow EF to use proxies to track status changes in your entities, and also to allow the use of Lazy Loading.

answered Dec 9, 2016 at 17:36

Diana

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1 Comment

Dimitri Over a year ago

Thank you sooo much Diana , i have seen the use of virtual properties quite a lot but i wan't teached that way so i really never got to it also changing from List<Subsribtion> to the inherrited type worked as well but im not sure why , why have inherritance if you can't use the base class as type ? Now i don't have the YogaClass/Workshop ID in my Subscribtion table , but a proper referenced ID in both inherrited classes tables. Thank you again ! Kind regards

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