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多列上的EF Core Linq连接引发NullReference异常

entity-framework-core asp.net-core linq entity-framework c#

Perrier · 技术社区 · 7 年前

我有一个相当难看的查询,只需要再扩展一个连接。查询生成然后抛出NullReferenceException运行时。当我在处理异常细节时,我在 TargetSite/CustomAttributes/Message = "The method or operation is not implemented." 但我不知道用哪种方法?

MarkedItems

EF核心版本为1.1.2。

查询:

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);

1 回复 | 直到 7 年前

Perrier 7 年前

多亏了这些评论,我才发现了我的问题所在。我以前没有意识到,库存(I)也可以为null,所以我必须检查null,即使市场项目中的I-s(不仅仅是m-s)也可以。

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);