实体框架 - 种子数据库 - PK需要包含在种子方法中吗？

Question

Following the MVC Music Store tutorial, the database is seeded with sample data. The Album class is as follows:

namespace MvcMusicStore.Models
{
    public class Album
    {
        public int      AlbumId     { get; set;}
        // ...
    }
}

Then in the sample data class that's used in the tutorial, an Album object is created like this within the Seed() method:

new Album { Title = "The Best Of Billy Cobham", 
Genre = genres.Single(g => g.Name == "Jazz"), 
Price = 8.99M, Artist = artists.Single(a => a.Name == "Billy Cobham"), 
AlbumArtUrl = "/Content/Images/placeholder.gif" }

In my project I have a class Tenant :

public class Tenant
{
    [key]
    public int      TenantId     { get; set;}
    // ...
}

In my Seed() method, I create a Tenant like this:

new Tenant { UserId=1,  UserName="Matthew" /*...*/ }

In my Seed() method I've included the Tenant PK which is UserId - Tenant is derived from User. I'm wondering, because in the Seed() method I've explicitly said that the Tenant's PK of UserId is 1, will that cause a problem when the method run? I ask because in the music store tutorial, the author hasn't included an Album's PK.

So the PK isn't explicitly stated when creating an Album. Will EF apply a PK by default? I've just spent a while creating quite a lot of sample data for my own project, and I've put the PK for a lot of entities in manually - will EF accept this or will it cause me problems? Is seeding the best way to generate sample data - alternatives?

Answer 1

When you don't add a [Key] attribute, EF will try to find an int readable - writeable property named Id or <yourClassName>Id .

That's all. And That's why AlbumId is taken as PK for class Album : No key attribute exists in that class, AlbumId = <nameOfClass>Id , it's a readable-writeable int.

If you have set a Key attribute, EF won't try to find another one. It's just a convention, which allow you to be less verbose.

For sample datas, Seed() method's body is a fine way to put them in Code First.