Tuesday, 20 July 2010

Using Entity Framework Code First (CTP4) in Dynamic Data

Following the sample EF CTP4 Walkthrough: Productivity Improvements you end up with a sample DbContext and of course I immediately thought of using this in Dynamic Data using the “ASP.NET Dynamic Data Entities Web Application” template (Figure 1),

Select ASP.NET Dynamic Data Entities Web Application

Figure 1 - Select ASP.NET Dynamic Data Entities Web Application

but I got the following error:

Error when using DbContext with DD4 EF Template.

Figure 2 – Error when using DbContext with DD4 EF Template.

This my my default code Listing 1

DefaultModel.RegisterContext(typeof(Models.ProductCatalog),
    new ContextConfiguration()
    {
        ScaffoldAllTables = true
    });

Listing 1 – my default DbContext registration

So I fired off an e-mail to Microsoft and was told “the guideline will be to use DD with DomainService, which will have full support of DbContext in the future” although that wont work out of the box at the moment so, I gave upBlushing

Then Diego Vega posted on twitter a link to Rowan Millers blog EF CTP4 Tips & Tricks: WCF Data Service on DbContext this turned out to be very useful, he talks about getting the underlying ObjectContext see Listing 2.

public class ProductCatalog : DbContext
{
    public ProductCatalog(String connectionString)
    {
        // set default connection string
        this.Database.Connection.ConnectionString = connectionString;
    }

    public ObjectContext UnderlyingContext
    {
        get { return this.ObjectContext; }
    }

    public DbSet<Category> Categories { get; set; }
    public DbSet<Product> Products { get; set; }
}

public class Category
{
    public string CategoryId { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Product> Products { get; set; }
}

public class Product
{
    public int ProductId { get; set; }
    public string Name { get; set; }
    public string CategoryId { get; set; }

    public virtual Category Category { get; set; }
}

Listing 2 – my ProductCatalog

In Listing 2 I use this feature to get the underlying ObjectContext (Also note my setting the connection string in the constructor). So now we have a cool way of getting Entity Framework Code First CTP4 working with Dynamic Data 4. This makes me very happyHappy Wizzard

So you will see that all we need to do to get this working with Dynamic Data now is to replace the

typeof(Models.ProductCatalog)

with

() => new Models.ProductCatalog(connectionString).UnderlyingContext

in the RegisterContext method to get at the underlying ObjectContext, which now leads us to Listing 3 .

public static void RegisterRoutes(RouteCollection routes)
{
    var connectionString = "Data Source=aragorn;Initial Catalog=ProductCatalog;Integrated Security=True";
    DefaultModel.RegisterContext(() => new Models.ProductCatalog(connectionString).UnderlyingContext,
        new ContextConfiguration()
        {
            ScaffoldAllTables = true
        });

    routes.Add(new DynamicDataRoute("{table}/{action}.aspx")
    {
        Constraints = new RouteValueDictionary(new { action = "List|Details|Edit|Insert" }),
        Model = DefaultModel
    });
}

Listing 3 – Global.asax RegisterRoutes method.

Now we can Edit, Update and Insert using Entity Framework Code First feature in CTP4.

Download

Nice: One of my favourite things about this is deployment of the DB is that if the DB does not exist on the server specified in the connection string the Entity Framework CTP4 will create it for you (or if you did not specify a connection string it will try to create it in the local SQL Express instance.
!Important: CTP5 make some minor API changes see Dabid Ebbo’s article here Using Dynamic Data with EF Code First and NuGet

5 comments:

Guillaume said...

Hi,

Thank you for your post it's just what I was waiting for before trying EF code first :)

Did you find a way to exclude the EdmMetadataSet table from the scaffodling?

Guillaume

Steve said...

Hi Guillaume, not sure about that, but I'll have a look.

Guillaume said...

I've just excluded it from the index page with a bit of Linq:
VisibleTables.Where(t => t.Name != "EdmMetadataSet") ;)

Steve said...

Ah Guillaume, got it, that is one of your tables yes :)

Steve

Steve said...

For EF5 see Using Dynamic Data with Entity Framework DbContext

Steve