Question

Currently I am building a web application with MVC 4 and Entity Framework code first scenario.

In the main structure of my application, I have a Dbcontext(BlogDB) to manage some Blog classes. It works fine as it created all the tables I need in the database. Then I created a Area to host an online store. My idea is to create a separated DbContext class(OnlineStoreDB) to handle the classes used for Online Store only.

My problem is once the OnlineStoreDB is fired, entity framework not only created tables for OnlineStore BUT ALSO removed old tables.

My questions are:

1. If you know a way to keep the old tables?
2. How exactly to manage the multi EF context classes in one application?

Code:

public class BlogDB : DbContext
{
    public BlogDB ()
        : base("DBConnection")
    {
        Database.SetInitializer(new BlogInitializer());
    }

    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Author> Authors { get; set; }
    public DbSet<Comment> Comments { get; set; }
}

public class OnlineStoreDB : DbContext
{
    public OnlineStoreDB() :
        base("DbConnection")
    {
        Database.SetInitializer(new OnlineStoreInitializer());
    }

    public DbSet<Order> Orders { get; set; }
    public DbSet<Product> Products { get; set; }
    public DbSet<User> Users { get; set; }
}

Answer 1

Xavier, welcome to code-first!

Yes, code-first was a brilliant approach that promised soooo much. But now you’ve hit the catch. There’s no clever mind at Microsoft (or outside as far as I know) who has come up with a smooth way to alter tables intelligently without endangering the data and possibly schema.

2 Years ago, the implementation strategy was to drop and re-build the DB. That was just intolerable as many of us didn’t have SU access and were stopped in our tracks.

For all the advantages I found from code first, I prefer DB first. While data can’t be preserved easily, annotations can through buddy classes.

Microsoft has come up with some clever Migration Strategies. I strongly suggest you read both articles. Code Project 2nd:

1) http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-code-based-migrations-walkthrough.aspx

2) http://www.codeproject.com/Articles/504720/EntityplusFrameworkplusCodeplusFirstplusMigrations

whether you decide to continue with Code-First, they should be enlightening. I sound like a critic but I’m torn between advantages of one and stability of the other.

Finally, I don’t think you should preserve 2 dbcontexts. Your POCOs should be consolidated under 1 context.