This question & answer lead me to believe that IQueryable require an active context for its operation. That means you should try this instead:
try
{
IQueryable<User> users;
using (var dataContext = new dataContext())
{
users = dataContext.Users.Where(x => x.AccountID == accountId && x.IsAdmin == false);
if(users.Any() == false)
{
return null;
}
else
{
return users.Select(x => x.ToInfo()).ToList(); // this line is the problem
}
}
}
catch (Exception ex)
{
...
}