join two tables in linq with special conditions - linq

Question

I hope one can help me, I am new in linq,
I have 2 tables name tblcart and tblorderdetail:
I just show some fields in these two tables to show whats my problem:
tblCart:
ID,
CartID,
Barcode,
and tblOrderDetail:
ID,
CartID,
IsCompleted
Barcode
when someone save an order, before he confirms his request,one row temporarily enter into the tblCart,
then if he or she confirms his request another row will be inserted into the tblOrderDetail ,
Now I wanna not to show the rows that is inserted into tblOrderDetailed(showing just temporarily rows which there is in tblCart),
In another words, if there is rows in tblCart with cartID=1 and at the same time there is the same row with CartID= 1 in tblOrderDetail, then I dont want that Row.
All in all, Just the rows that there isnt in tblOrderDetail, and the field to realize this is CartID,
I should mention that I make Iscompleted=true, and with that either we can exclude the rows we do not want,
I did this:
var cartItems = context.tblCarts
.Join(context.tblSiteOrderDetails,
w => w.CartID,
orderDetail => orderDetail.cartID,
(w,orderDetail) => new{w,orderDetail})
.Where(a=>a.orderDetail.cartID !=a.w.CartID)
.ToList()
however it doesn't work.
one example:
tblCart:
ID=1
CartID=1213
Barcode=4567
ID=2
CartID=1214
Barcode=4567
ID=3
CartID=1215
Barcode=6576
tblOrderDetail:
ID=2
CartID=1213
Barcode=4567
IsCompleted=true
with these data it should just show the last two Row in tblCart, I mean
ID=2
CartID=1214
Barcode=4567
ID=3
CartID=1215
Barcode=6576

Answer 1

This sounds like a case for WHERE NOT EXISTS in sql.
roughly translated this should be something like this in LINQ:
var cartItems = context.tblCarts.Where(crt => !context.tblSiteOrderDetails.Any(od => od.CartID == crt.cartID));

Answer 2

If you have a navigation property on cart to reference details (I'll assume it's called Details), then:
var results=context.tblCarts.Where(c=>!c.Details.Any(d=>d.IsCompleted));