Question

I come from the web forms world, and I’m learning MVC4 and Entity Framework 5 with a code-first approach. This is my first time using EF code-first and I’m having some trouble understanding what EF needs from me to be able to create/update a database.

I’m making a request to a RESTful service and deserializing the response into a DataContract. Ideally, I would like to be able to insert this DataContract into a database but I’m unsure how to generate the DbContext classes from the DataContract so EF can do it’s thing.

The simplified version of the DataContract…

[DataContract]
public class MoviesDataContract {
    [DataMember(Name = "total")]
    public int Total { get; set; }

    [DataMember(Name = "movies")]
    public IEnumerable<Movie> Movies { get; set; }

    [DataMember(Name = "link_template")]
    public string LinkTemplate { get; set; }
}

[DataContract]
public class Movie {
    [DataMember(Name = "id")]
    public int Id { get; set; }

    [DataMember(Name = "title")]
    public string Title { get; set; }

    [IgnoreDataMember]
    public int? Year {
        get {
            int i;
            return int.TryParse(_year, out i) ? i : (int?)null;
        } 
        set { _year = value.ToString(); }
    }

    [DataMember(Name = "year")]
    private string _year { get; set; }
}

Here’s an example of the DataContract usage…

using(var response = (HttpWebResponse)request.GetResponse()) {
    var serializer = new DataContractJsonSerializer(typeof (MoviesDataContract));
    var dataContract = (MoviesDataContract)serializer.ReadObject(response.GetResponseStream());

    var model = new List<MovieViewModel>();
    dataContract.Movies.ToList().ForEach(movie => model.Add(new MovieViewModel {
        Title = movie.Title,
        Year = movie.Year
    }));

    // MovieDbContext doesn't exist and it's what I'm unsure of how to generate
    // I would think it would work something like this though (once created)
    var db = new MovieDbContext();
    db.Add(dataContext);
    db.SaveChanges();

    return View(model);
}

My Questions are…

1. Is there a way to generate the DbContext classes from my DataContract or do I need to manually create them?
2. Is there a better approach to using (or really saving to a db) Deserialized data with Entity Framework (especially EF5)?
3. Could someone provide a link that discusses EF (4 or higher) being used in conjunction with a DataContract? I think I may not have a complete grasp on how to effectively use EF5.

Answer 1

Have you tried feeding your data contracts to DBSet’s like you would when starting a normal code-first project?

public class ProductContext : DbContext

{

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

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

}

EF should ignore the existing attributes and create some entities.

See this article for a good example of how to work with DataContext: http://msdn.microsoft.com/en-us/jj729737

Since you’re new to EF you might as well start here: http://msdn.microsoft.com/en-us/ee712907