Asp.net core 使用linq从实体框架核心获取{“error”：“Sql树中的Null TypeMapping”}

我有这个linq select语句，我得到了这个错误{“error”：“Sql树中的Null TypeMapping”}

我会把代码放在下面，但有没有办法获得更多关于问题所在的信息？ 如果您需要实体，请告诉我，我会复制它们

问候

var query = from o in _orderDataDbContext.tblSellFlangeOrders
            join od in _orderDataDbContext.tblSellFlangeOrderDetails
            on (int?)o.Id equals od.SellFlangeOrderId
            join t in _orderDataDbContext.tblTypes
            on od.TypeId equals (int?)t.Id
            join l in _orderDataDbContext.VLegendeFlangeLengths
            on od.LengthId equals (int?)l.Id
            join g in _orderDataDbContext.VLegendeGrades
            on od.GradeId equals (int?)g.Id
            where o.Id == request._flangeOrderID
                        select new FlangeOrderDetailByPoCodeDto
                        {
                            SellFlangeOrderID = o.Id,
                            DetailID = od.Id,
                            Price = od.Price1000,
                            BF = od.Bf,
                            TypeID = t.Id,
                            Type = t.Inches1 + "x" + t.Inches2,
                            LengthID = l.Id,
                            Length = l.Length + "'" + l.OverLength + "\"",
                            GradeID = g.Id,
                            Grade = g.Grade
                        };

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可能的副本I未能再现该问题。如果您希望社区审查和调试代码，请显示相关实体和DbContext。这是否回答了您的问题？