Why does an EntityCollection sometimes expose extension methods and sometimes not?

I'm trying to make some changes to our Entity Framework model, which is causing me massive trouble at the moment - the idea is to change a 1:1 relationship between two databases into a many-many relationship. If you make the change in EF and then rebuild the database the object it generates to represent this relationship is - unsurprisingly - an EntityCollection instead of a single type object.

For the moment I've been running through all the errors that this change generates and altering DatabaseObject references to DatabaseObject.ElementAt(0) just so I can get it to build. However one set of references won't seem to giv开发者_C百科e me the extension methods on EntityCollection that allow one to operate on a collection - things like ElementAt(), Select(), First() and so on, and I can't see why.

In instances that work, the object is generated from a base class which is then inherited:

            _task = _customersRepository.GetDeepTask(taskId);
            _customerService = _task.CustomerServiceFeature.CustomerService;

           //then in class which inherits above code

           string conStr = customerService.DatabaseObject.ElementAt(0).GetConnectionString(_customerService);

But in the instance that doesn't give me the extension methods, it's generated like this:

    public void Execute(ScheduledTask task)
    {
        CustomerService service = task.CustomerServiceFeature.CustomerService;
        //this errors and doesn't offer extension methods
        string ConnectionString = service.DatabaseObject.GetConnectionString(service);
    }

I can't see why these two instances are behaving differently?

Cheers, Matt

You need a using declaration for the namespace containing the extension method's classes.

E.g. to see Select, Where extension methods on IEnumerable<T> and IQueryable<T> there needs to be a

using System.Linq;

in your code.