Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?
- by DanM
I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this:
public IEnumerable<Person> SelectPersons()
{
using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person))
{
return repository.GetAll();
}
}
This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example:
var persons = gateway.SelectPersons();
// Dispose() is fired here
var personViewModels = (
from b in persons
select new PersonViewModel
{
Id = b.Id,
Name = b.Name,
Age = b.Age,
OrdersCount = b.Order.Count()
}).ToList(); // executes queries
In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called.
So, a couple questions:
How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>?
What does Dispose() actually do?
I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?
