How to reference the same table twice? - linq

Question

First of all I have to admit I'm very much a novice in Linq and Lambda expressions.
I'm trying to get the following SQL statement into a Linq statement (using lamda expressions):
select *
from dbo.tblStockTransfers t1,
dbo.tblSuppliers t2
where t1.SupplierID = t2.SupplierID
and t2.WarehouseID in (1,2,3)
and t1.GoodsPickedUp = 1
and Not exists
(select 1 from dbo.tblStockTransfers t3
where t3.TransferOutID = t1.TransferID and t3.TransferConfirm = 1)
My class StockTransfer is an aggregate root and has it's own repository.
Now so far I got the following (the variable allowedWarehouses contains the list of warehouse IDs):
Return GetObjectSet().Where(Function(st) allowedWarehouses.Contains(st.Supplier.WarehouseID) And st.GoodsPickedUp = True)
This works fine, but obviously is missing the " and not exists ..." part (the last 3 lines of the SQL code at the top of this posting).
I know that Linq doesn't have a "not exists", but you can use the "Any" method for this.
Here's a working example of this elsewhere in my code:
Return GetObjectSet().Where(Function(sw) sw.Active = True And Not sw.Suppliers.Any(Function(sp) sp.WarehouseID = sw.Id))
This works fine and will give me any warehouses which are not linked to a supplier yet.
As you can see in the above example this is fine as I'm referring to the related table "Suppliers".
However, in the SQL code I'm now trying to convert into Linq, the "not exists" is not on a linked table but on itself. Is there a way I can create a 2nd reference on the main table and use that in a ".. not ..any" part. Maybe something like:
Return GetObjectSet().Where(Function(st) allowedWarehouses.Contains(st.Supplier.WarehouseID) And st.GoodsPickedUp = True And Not st2.Any(st2.TransferOutID = st.TransferId and st2.TransferConfirm = true)
But I don't know how to define st2 (i.e. in this case st2 would be a 2nd alias to StockTransfer).
Any Help would be greatly appreciated.

Answer 1

This is not the answer to the question, but it is a work-around which does get me the result I need:
Dim st1 As List(Of StockTransfer) = GetObjectSet.Where(Function(st) allowedWarehouses.Contains(st.Supplier.WarehouseID) And st.GoodsPickedUp = True).ToList
Dim st2 As List(Of StockTransfer) = GetObjectSet.Where(Function(st) st.TransferConfirm = True).ToList
For Each st As StockTransfer In st2
st1.RemoveAll(Function(x) x.Id = st.TransferOutID)
Next
Return st1
I'm obviously cheating by splitting out the query in 2 parts, where each part ends up in a list and then I remove from list 1 any items which I've got in list 2 (removing the ones which would normally be ignored by the "not exists" part).
However, I would love to hear it if anyone can come up with a working solution using Linq and lambda expressions (as this does feel a bit like a cheat).

Answer 2

I would do it something like this:
Dim lsWareHouseIds As New List(Of Integer)() From {1,2,3}
dim obj= ( _
From t1 in db.tblStockTransfers _
join t2 in db.tblSuppliers _
on t1.SupplierID equals company.SupplierID _
where lsWareHouseIds.Contains(t2.WarehouseID) _
andalso t1.GoodsPickedUp =1 _
andalso Not _
(
from t3 in db.tblStockTransfers _
where t3.TransferConfirm=1 _
select t3.TransferOutID _
).Contains(t1.TransferID) _
select t1 _
)
I did see you comment and you answer. Can't you do like this:
GetObjectSet.Where(Function(st) _
allowedWarehouses.Contains(st.Supplier.WarehouseID) And st.GoodsPickedUp = True _
Andalso Not _
GetObjectSet.Where(Function(st) _
st.TransferConfirm = True).Any(Function(x) x.Id = st.TransferOutID)).ToList