Question

In my previous applications when I used linq-to-sql I would always use one class to put my linq-to-sql code in, so I would only have one DataContext.

My current application though is getting too big and I started splitting my code up in different classes (One for Customer, one for Location, one for Supplier…) and they all have their own DataContext DatabaseDesignDataContext dc = new DatabaseDesignDataContext();

Now when I try to save a contact with a location (which I got from a different DataContext) I get the following error:

“An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported.”

I assume this is because I create a DataContext for every class, but I wouldn’t know how to this differently?

I’m looking for any ideas, thanks.

My classes look like the following:

 public class LocatieManagement
{
    private static DatabaseDesignDataContext dc = new DatabaseDesignDataContext();

    public static void addLocatie(locatie nieuweLocatie)
    {
        dc.locaties.InsertOnSubmit(nieuweLocatie);
        dc.SubmitChanges();
    }

    public static IEnumerable<locatie> getLocaties()
    {
        var query = (from l in dc.locaties
                     select l);
        IEnumerable<locatie> locaties = query;

        return locaties;
    }

    public static locatie getLocatie(int locatie_id)
    {
        var query = (from l in dc.locaties
                     where l.locatie_id == locatie_id
                     select l).Single();

        locatie locatie = query;
        return locatie;

    }
}

Answer 1

Another solution I found for this is to create one parent class DataContext

public class DataContext
{
    public static DatabaseDesignDataContext dc = new DatabaseDesignDataContext();
}

And let all my other classes inherit this one.

 public class LocatieManagement : DataContext
 {
        public static void addLocatie(locatie nieuweLocatie)
        {
            dc.locaties.InsertOnSubmit(nieuweLocatie);
            dc.SubmitChanges();
        }
 }

Then all the classes use the same DataContext.