Attach additional ObjectSets to ObjectContext from separate project

Question

I hope this makes sense. I have a ASP.NET web application that uses Entity Framework. I have added a couple of custom tables to the db and created a separate project to handle the CRUD operations for those tables. I chose the separate project because I don't want future upgrades to the application to overwrite my custom features.

My problem is this. How do I attach/combine my custom ObjectContext to the ObjectContext of the application? I want to use the same UnitOfWorkScope (already in the application) to maintain the one ObjectContext instance per HTTP request. Again, I don't want to add my ObjectSets to the application's ObjectContext for my reason listed above.

Here is some code:

Widget.cs

public partial class Widget
{
public Widget()
{
}
public int WidgetId {get;set;}
public string WidgetName {get;set;}
}

WidgetObjectContext.cs

public partial class WidgetObjectContext : ObjectContext
{
private readonly Dictionary<Type, object> _entitySets;

public ObjectSet<T> EntitySet<T>()
where T : BaseEntity
{
var t = typeof(T);
object match;
if(!_entitySets.TryGetValue(t, out match))
{
match = CreateObjectSet<T>();
_entitySets.Add(t, match);
}
return (ObjectSet<T>)match;
}

public ObjectSet<Widget> Widgets
{
get
{
if((_widgets == null))
{
_widgets = CreateObjectSet<Widget>();
}
return _widget;
}
}
private ObjectSet<Widget> _widgets;

In my WidgetManager class if I was using the application's ObjectContext I would query my tables like this:

var context = ObjectContextHelper.CurrentObjectContext;
var query = from c in context.ObjectSet .... etc

What I want would be to do something like this:

var context = ObjectContextHelper.CurrentObjectContext.Attach(WidgetObjectContext);

I know this won't work but that is the gist of what I am trying to accomplish. Hope this is clear enough. Thanks.

Answer 1

I don't think it is possible. ObjectContext creates entity connection which connects to metadata describing mapping and database. But you have to different sets of metadata - one for ASP.NET application and one for separate project. Simply you need two connection to work with these models => you need two ObjectContexts.

Answer 2

FYI: The previous answer was correct at the time of the answer. It is now possible to do this using the DbContext available in EF 4.1. The caveat is that you must use the code-first strategy in order to build your custom context. In other words, you won't be able to use EDMX files to accomplish this.