英孚核心Linq加入多列拋出NullReference異常

Question

我有一個相當醜陋的查詢，只需要擴展一個更多的聯接。查詢構建然後引發NullReferenceException運行時。由於我在例外的細節上掙扎，我在TargetSite/CustomAttributes/Message = "The method or operation is not implemented."找到了這條消息，但我不知道哪種方法？

MarkedItems是新的連接，我認爲問題可能是多列連接，或者我不得不將新表添加到group by子句中。相同的查詢使用EF6在LinqPad中運行，所以這必須是EF7中尚未實現的東西。

EF核心版本是1.1.2。

查詢：

var inventory = (from it in _ctx.Items 
        join i in _ctx.Inventories on it.Id equals i.ItemId into iit 
        from i in iit.DefaultIfEmpty() 
        join m in _ctx.MarkedItems on 
         new { 
           eancode = i.EANCode, 
           projectid = i.ProjectId 
          } 
         equals new { 
          eancode = (m != null ? m.EANCode : string.Empty), 
          projectid = (m != null ? m.ProjectId : Guid.Empty) 
         } into im 
        from m in im.DefaultIfEmpty()      
        where it.ProjectId == cmp.ProjectId 
        group i by new { 
         EANCode = it.EANCode, 
         ItemNo = it.ItemNo, 
         Name = it.Name, 
         BaseQty = it.BaseQty, 
         Price = it.Price, 
         m = (m != null ? m.EANCode : null) 
        } into lg 
        select new ComparisonBaseModel() { 
          EANCode = lg.Key.EANCode, 
          ItemName = lg.Key.Name, 
          Price = lg.Key.Price, 
          ScanQty = lg.Sum(s => s != null ? s.ScanQty : 0), 
          BaseQty = lg.Key.BaseQty, 
          DiffQty = lg.Sum(s => s != null ? s.ScanQty : 0) - lg.Key.BaseQty, 
          DiffPrice = lg.Key.Price * (lg.Sum(s=> s!= null ? s.ScanQty : 0) - lg.Key.BaseQty), 
          AllTasked = !lg.Any(s=>(s != null && s.InventoryTaskId == null) || s==null), 
          Flagged = lg.Key.m != null 
        }).Where(x=>x.DiffQty != 0); 

Answer 1

多虧了我能找到我的查詢，真正的問題的意見。我之前並沒有意識到，庫存（i）也可能爲空，因此我必須檢查MarketItems加入中的i-s（不僅是m-s）是否爲空值。

不知道這是否對任何人都有幫助，但是在我遇到EF7/EF6的一些差異之後，錯誤消息會讓人誤解。

var inventory = (from it in _ctx.Items 
        join i in _ctx.Inventories on it.Id equals i.ItemId into iit 
        from i in iit.DefaultIfEmpty() 
        join m in _ctx.MarkedItems on 
         new { 
           eancode = (i != null ? i.EANCode : string.Empty), 
           projectid = (i != null ? i.ProjectId : Guid.Empty) 
          } 
         equals new { 
          eancode = (m != null ? m.EANCode : string.Empty), 
          projectid = (m != null ? m.ProjectId : Guid.Empty) 
         } into im 
        from m in im.DefaultIfEmpty()      
        where it.ProjectId == cmp.ProjectId 
        group i by new { 
         EANCode = it.EANCode, 
         ItemNo = it.ItemNo, 
         Name = it.Name, 
         BaseQty = it.BaseQty, 
         Price = it.Price, 
         m = (m != null ? m.EANCode : null) 
        } into lg 
        select new ComparisonBaseModel() { 
          EANCode = lg.Key.EANCode, 
          ItemName = lg.Key.Name, 
          Price = lg.Key.Price, 
          ScanQty = lg.Sum(s => s != null ? s.ScanQty : 0), 
          BaseQty = lg.Key.BaseQty, 
          DiffQty = lg.Sum(s => s != null ? s.ScanQty : 0) - lg.Key.BaseQty, 
          DiffPrice = lg.Key.Price * (lg.Sum(s=> s!= null ? s.ScanQty : 0) - lg.Key.BaseQty), 
          AllTasked = !lg.Any(s=>(s != null && s.InventoryTaskId == null) || s==null), 
          Flagged = lg.Key.m != null 
        }).Where(x=>x.DiffQty != 0);