How do I sort on a column that isn't in the database with LINQ to entities?

LINQ to Entities 3.5 doesn't support String.Join so I'm binding my gridview to a property I define outside the Select statement. Obviously it's not letting me sort on RecipientNames because it's开发者_C百科 just an IEnumerable and that doesn't make sense. How can I use LINQ to Entities to sort on my new column? If possible I'd like to get rid of RecipientNamesList altogether and create something that LINQ will be able to handle for sorting.

IQueryable<NotificationDetail> resultsFlattened = results.Select(n => new NotificationDetail() 
{
..
RecipientNames = n.NotificationRecipients.Select(nr => nr.Recipient.RecipientNameFirst + " " + nr.Recipient.RecipientNameLast).Where(s => s.Trim().Length > 0)});
});

IQueryable<NotificationDetail> resultsPaged = ApplySortingPaging(resultsFlattened,SortPageOptions);

return resultsPaged.ToEntityList(results.Count()); //blows up here, obviously

public string RecipientNamesList
{
    get
    {
          return String.Join(", ", RecipientNames.ToArray());
    }
}

It blows up because the sort cannot be translated into SQL. The easy solution is to make sure you perform the sort locally and not in SQL Server. Just add a ToList or AsEnumerable after the first query.

resultsFlattened = resultsFlattened.ToList(); 

You'll want to ensure that you do your paging before this, otherwise you could be pulling down a large number of rows from the database.

Or you use the Linq.Translations library developed by by Damien Guard and others. It enables you to use local, calculated properties just as you require.