Question

So I have 2 IQueryable<Array> queries with a common string type; I want to use the second query to remove all records using the common type in the first, leaving only the records not found as the result of the first query. Not quite sure how to do it.

Answer 1

The most understandable way to do it is to filter out the items in ListA using Where():

IQueryable<LISTA> as = db.ListA.Where(x => x.Active);
IQueryable<LISTB> bs = db.ListB.Where(x => x.HadReview);
as = as.Where(a => bs.Any(b => a.LogginID == b.LogginID) == false);

A way that might be more efficient is to use a Group Join:

var as = from a in db.ListA.Where(x => x.Active)
         join b in db.ListB.Where(x => x.HadReview) 
             on a.LogginID equals b.LogginID into bs
         where bs.Any() == false
         select a;

Edit: If you have two different DataContexts the above will not work. This might:

IQueryable<LISTA> as = db1.ListA.Where(x => x.Active);
IQueryable<LISTB> bs = db2.ListB.Where(x => x.HadReview);
as = as.Where(a => bs.Select(b => b.LogginID).Contains(a.LogginID) == false);

See also: Linq to SQL – How to inner join tables from different Data Context?