Linq GROUP & SUM the same columns from different tables - linq

Question

I'm trying to combine these 2 Linq queries into 1:
var query = from s in _context.Set<StockInventoryItem>()
where s.StockCatalogueItemId == id
group s by s.StockType into g
select new
{
inStock = g.Sum(x => x.QtyInStock),
};
var query2 = from p in _context.Set<PurchaseOrderItem>()
where p.StockCatalogueItemId == id
group p by p.StockType into g2
select new
{
onOrder = g2.Sum(x => x.QtyStillDue)
};
Note that the filtering, grouping and output is the same from both tables, and I want the results to look like this:
StockType inStock onOrder
+----------+--------+--------+
Type 1 4 3
+----------+--------+--------+
Type 2 0 1
i.e. Quantities grouped by StockType
This is EF code first and there is no direct relationship between these tables, which is why I'm trying this query in the service layer so I can access both entities.

Answer 1

You should be able to "shoehorn" both groups into the same sequence with anonymous types and Concat, and then count the results separately, like this:
var query = _context.Set<StockInventoryItem>()
.Where(ii => ii.StockCatalogueItemId == id)
.Select(ii => new {
II = ii, PO = (PurchaseOrderItem)null
}).Concat(_context.Set<PurchaseOrderItem>()
.Where(po => po.StockCatalogueItemId == id)
.Select(po => new {
II = (StockInventoryItem)null, PO = po
})).GroupBy(p => II != null ? ii.StockType : PO.StockType)
.Select(g => new {
InStock = g.Sum(p => p.II != null ? p.II.QtyInStock : 0)
, OnOrder = g.Sum(p => p.PO != null ? p.PO.QtyStillDue: 0)
});