linq System.ObjectDisposedException

Question

Hi, i have a problem with some data i retrievied from db with linq. When I try to access data I obtain the following exception: System.ObjectDisposedException : The istance of ObjectContext was deleted and is not possible to use it again for action that need a connection. This is the code:

using (ProvaDbEntities DBEntities =
new ProvaDbEntities(Utilities.ToEntitiesConnectionString()))

            {
                ObjectQuery<site> sites = DBEntities.site;

                IEnumerable<site> q = from site in sites

                                      select site;


                {
                    ObjectQuery<auction> auctions = DBEntities.auction;

                    IEnumerable<auction> q1 = from auction in auctions

                                              where auction.site == this.Name

                                              select auction;

                    IEnumerable<IAuction> res = q1.Cast<IAuction>();

                    return res;

            }
        }
        catch(Exception e)
        {
            throw new UnavailableDbException("[GetAuctions]" + e.Message);
        }

Someone can help me??? Tanks Fabio

Answer 1

Yes - you're returning a result which will be lazily evaluated - but you're disposing of the data context which would be used to fetch the results.

Options:

• Load the results eagerly, e.g. by calling ToList on the result
• Don't dispose of the context (I don't know what the situation is in the Entity Framework; you could get away with this in LINQ to SQL, but it may not be a good idea in EF)
• Dispose of the context when you're finished with the data

In this case I'd suggest using the first option - it'll be safe and simple. As you're already filtering the results and you're casting to IEnumerable<IAuction> anyway, you're unlikely to get the normal downsides of materializing the query early. (If it were still IQueryable<T>, you'd be throwing away the ability to add extra bits to the query and them still be translated to SQL.)