如何在linq中使用“COALESCE（SUM ...”？

Question

我尝试使用sum和Coalesce。我怎样才能翻译成linq？

 SELECT @SumQtyOut=COALESCE(SUM(Qty),0) FROM dbo.StockMovement WHERE FromLocationType=@FromLocationType AND
         * FromNo=@FromNo AND FromSeq=@FromSeq AND ItemTypeNo=@ItemTypeNo AND ItemID=@ItemID

我做了些事：

 using (StockProcedureDataContext stock = new StockProcedureDataContext())
                {
                    SumQtyOut = from s in stock.StockMovements 
                                where s.FromLocationType == FromLocationType &&
                                s.FromNo== FromNo && 
                                s.FromSeq == FromSeq &&
                                s.ItemTypeNo == ItemTypeNo &&
                                s.ItemID == ItemID select 
                }

Answer 1

此代码段应该会产生您要查找的结果。

using (StockProcedureDataContext stock = new StockProcedureDataContext())
{
    var items = from s in stock.StockMovements 
                where s.FromLocationType == FromLocationType &&
                s.FromNo== FromNo && 
                s.FromSeq == FromSeq &&
                s.ItemTypeNo == ItemTypeNo &&
                s.ItemID == ItemID 
                select s.Qty ?? 0;
    SumQtyOut = items.Sum(x => x);
}

如果select s.Qty ?? 0为s.Qty，则

null会返回0。 items.Sum(x => x)总结了您选择的数量。