ASP MVC Entity Framework Code first model using existing class

Question

Know the title is a bit vague and not very descriptive for my real question, but here goes.

I have a new ASP MVC project, where I have EF setup. It is working like a charm. Now I would like to create a new code first model which I'm going to use to store RSS feed items.

Instead of creating the model from scratch, I would very much like to use System.ServiceModel.Syndication.SyndicationItem as a basis for my model. I might want to add some custom fields, but for now I can pretty much use the exact same fields and field types.

My question then is, can I inherit from this class into my code first model? or do I have to make the exact same fields and field types double up?

I don't see any reason why this would not work, EF usually is not too constraining towards the entity types used in the model. — DevilSuichiro
– DevilSuichiro, Commented Sep 6, 2017 at 15:45

corix010 · Accepted Answer · 2017-09-06 20:00:57Z

1

If it's only SyndicationItem and SyndicationCategory that you're after and don't care about ignoring some properties, you can try the following:

public class FeedItem : SyndicationItem
{
    [Key]
    public int Id { get; set; }

    // additional properties go here
}

public class MyContext : DbContext
{
    public MyContext()
        : base("name=MyContext")
    {

    }

    public DbSet<FeedItem> FeedItems { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<FeedItem>().HasKey<int>(f => f.Id);
        modelBuilder.Entity<SyndicationCategory>().HasKey(c => c.Name);

        // Ignore entities
        modelBuilder.Ignore<SyndicationPerson>();
        modelBuilder.Ignore<SyndicationLink>();
        modelBuilder.Ignore<SyndicationContent>();
        modelBuilder.Ignore<SyndicationElementExtension>();

        // Ignore properties
        modelBuilder.Entity<FeedItem>().Ignore(f => f.AttributeExtensions);
    }
}

edited Sep 6, 2017 at 20:00

answered Sep 6, 2017 at 16:01

corix010

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2 Comments

Martin at Mennt Over a year ago

I tried that with no luck. But I guess I also have to create the other related classes as code first models. Ex. screencast.com/t/CSXxu2DKW

Martin at Mennt Over a year ago

Yes, this works. But I would like to include the categories too.

Martin at Mennt · Accepted Answer · 2017-09-06 15:52:10Z

Okay, I tried this.

Model

namespace App.Models
{
    public class FeedItem : System.ServiceModel.Syndication.SyndicationItem
    {
    }
}

DB Context

namespace App.DAL
{
    public partial class DbContext : IdentityDbContext<ApplicationUser>
    {
        public DbContext() : base("name=DbContext")
        {
        }

        public static DbContext Create()
        {
            return new DbContext();
        }

        public DbSet<FeedItem> FeedItems { get; set; }
    }
}

And got this in return when running the app.

App.DAL.SyndicationPerson: : EntityType 'SyndicationPerson' has no key defined. Define the key for this EntityType. App.DAL.SyndicationElementExtension: : EntityType 'SyndicationElementExtension' has no key defined. Define the key for this EntityType. App.DAL.SyndicationCategory: : EntityType 'SyndicationCategory' has no key defined. Define the key for this EntityType. App.DAL.SyndicationLink: : EntityType 'SyndicationLink' has no key defined. Define the key for this EntityType. SyndicationContents: : The referenced EntitySet 'SyndicationContents' for End 'FeedItem_Copyright_Target' could not be found in the containing EntityContainer. SyndicationContents: : The referenced EntitySet 'SyndicationContents' for End 'SyndicationFeed_Copyright_Target' could not be found in the containing EntityContainer. SyndicationContents: : The referenced EntitySet 'SyndicationContents' for End 'SyndicationFeed_Description_Target' could not be found in the containing EntityContainer. SyndicationContents: : The referenced EntitySet 'SyndicationContents' for End 'SyndicationFeed_Title_Target' could not be found in the containing EntityContainer. SyndicationContents: : The referenced EntitySet 'SyndicationContents' for End 'FeedItem_Summary_Target' could not be found in the containing EntityContainer. SyndicationContents: : The referenced EntitySet 'SyndicationContents' for End 'FeedItem_Title_Target' could not be found in the containing EntityContainer. SyndicationPersons: EntityType: EntitySet 'SyndicationPersons' is based on type 'SyndicationPerson' that has no keys defined. SyndicationElementExtensions: EntityType: EntitySet 'SyndicationElementExtensions' is based on type 'SyndicationElementExtension' that has no keys defined. SyndicationCategories: EntityType: EntitySet 'SyndicationCategories' is based on type 'SyndicationCategory' that has no keys defined. SyndicationLinks: EntityType: EntitySet 'SyndicationLinks' is based on type 'SyndicationLink' that has no keys defined. SyndicationContents: EntityType: EntitySet 'SyndicationContents' is based on type 'SyndicationContent' that has no keys defined.

I might have missed something.

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