Question

I’m pretty new to using Entity Framework, as well as to using ASP.NET MVC. I’ve been able to complete a couple of tutorials on the ASP.NET MVC website and thought I would start my own project based on the MVC Music Store application.

I can’t tell where I went wrong (it all looks the same to me), but for some reason my seed data isn’t creating the database.

Item class:

namespace MySite.Models
{
    public class Item
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}

Tag class:

namespace MySite.Models
{
    public class Tag
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}

ItemTag class:

namespace MySite.Models
{
    public class ItemTag
    {
        public int Id { get; set; }
        public int ItemId { get; set; }
        public int TagId { get; set; }
    }
}

MySiteEntities class:

namespace MySite.Models
{
    public class MySiteEntities : DbContext
    {
        public DbSet<Item> Items { get; set; }
        public DbSet<Tag> Tags { get; set; }
        public DbSet<ItemTag> ItemTags { get; set; }
    }
}

Global.asax class:

namespace MySite
{
    public class MvcApplication : System.Web.HttpApplication
    {
        ...

        protected void Application_Start()
        {
            System.Data.Entity.Database.SetInitializer(new MySite.Models.SampleData());

            AreaRegistration.RegisterAllAreas();

            RegisterGlobalFilters(GlobalFilters.Filters);
            RegisterRoutes(RouteTable.Routes);
        }
    }
}

Web.config file:

<configuration>
  ...

  <connectionStrings>
    <add name="MySiteEntities"
      connectionString="Data Source=|DataDirectory|MySite.sdf"
      providerName="System.Data.SqlServerCe.4.0" />
  </connectionStrings>
</configuration>

SampleData class:

namespace MySite.Models
{
    public class SampleData : DropCreateDatabaseIfModelChanges<MySiteEntities>
    {
        protected override void Seed(MySiteEntities context)
        {
            new List<Item>
            {
                new Item { Id = 1, Name = "Bob Jones" },
                new Item { Id = 2, Name = "George Smith" },
                new Item { Id = 3, Name = "Boys and Girls" },
                new Item { Id = 4, Name = "The President's Hair" },
                new Item { Id = 5, Name = "Invaders From Mars" },
                new Item { Id = 6, Name = "Tank Shooter" },
                new Item { Id = 7, Name = "Stew's Blog" },
                new Item { Id = 8, Name = "Social Mania" }
            }.ForEach(i => context.Items.Add(i));

            new List<Tag>
            {
                new Tag { Id = 1, Name = "Author" },
                new Tag { Id = 2, Name = "Movie" },
                new Tag { Id = 3, Name = "Video Game" },
                new Tag { Id = 4, Name = "Website" }
            }.ForEach(t => context.Tags.Add(t));

            new List<ItemTag>
            {
                new ItemTag { Id = 1, ItemId = 1, TagId = 1 },
                new ItemTag { Id = 2, ItemId = 2, TagId = 1 },
                new ItemTag { Id = 3, ItemId = 3, TagId = 2 },
                new ItemTag { Id = 4, ItemId = 4, TagId = 2 },
                new ItemTag { Id = 5, ItemId = 5, TagId = 3 },
                new ItemTag { Id = 6, ItemId = 6, TagId = 3 },
                new ItemTag { Id = 7, ItemId = 7, TagId = 4 },
                new ItemTag { Id = 8, ItemId = 8, TagId = 4 }
            }.ForEach(x => context.ItemTags.Add(x));
        }
    }
}

That’s pretty much everything. I did delete the database file at one point. Shouldn’t it get created again when I build the solution?

Answer 1

Reason: This is because you are using “DropCreateDatabaseIfModelChanges“.

As it indicates if your model doesn’t change then it wont create the database (or if the DB is already there then it wont add your populated data).

Solution: You want to use “CreateDatabaseIfNotExists” instead.

Alternative: If you’re DB is already created and you just want to add initial data then use “DropCreateDatabaseAlways” HOWEVER you must realise this will recreate the DB from scratch every time an application restarts. So only use this when your DB is already created and you don’t want to change the model (and you don’t care about losing the data already in the DB) AND then change it to one of the other two options.