如何在 select 子句中创建匿名类型列表？

Question

这是我在项目中使用的查询之一：

var carQuery = from cars in context.Cars
                           .Where(c => c.CarID==3)
                           from stockTypes in context.StockTypes
                            .Where(st => cars.StockTypeId == st.StockTypeID).DefaultIfEmpty()
                           from carUnit in context.Car_Units
                           .Where(cu => cu.CarId == cars.CarID).DefaultIfEmpty()
                           from carAttributes in context.Car_Attributes
                           .Where(ca => ca.CarId == cars.CarID).DefaultIfEmpty()
                           from attribute in context.Attributes
                           .Where(attr => attr.AttributeId==carAttributes.AttributeId).DefaultIfEmpty()

                           select new
                           {
                               CarID = cars.CarID,
                               CarName = cars.CarName,
                               CarDescription = cars.CarDescription,
                               StockType = (stockTypes == null) ? null : new
                               {
                                   StockTypeID = stockTypes.StockTypeID,
                                   StockName = stockTypes.StockName
                               },
                               IsActive = cars.IsActive,
                               IsCab = cars.IsCab,
                               Unit = (carUnit == null) ? null : new
                               {
                                   Id = carUnit.UnitId,
                                   Name = carUnit.Unit.UnitName
                               },
                               Attributes = attribute
                           };

如果 context.Attributes 返回多行，则整个结果集也返回多行。

是否有可能将具有多个属性的单一汽车类型作为汽车的属性列表返回？

请帮忙。

谢谢， 马赫什

Answer 1

您只需将属性查询移动到结果集中：

        var carQuery = from cars in context.Cars
                       .Where(c => c.CarID==3)
                       from stockTypes in context.StockTypes
                        .Where(st => cars.StockTypeId == st.StockTypeID).DefaultIfEmpty()
                       from carUnit in context.Car_Units
                       .Where(cu => cu.CarId == cars.CarID).DefaultIfEmpty()
                       from carAttributes in context.Car_Attributes
                       .Where(ca => ca.CarId == cars.CarID).DefaultIfEmpty()

                       select new
                       {
                           CarID = cars.CarID,
                           CarName = cars.CarName,
                           CarDescription = cars.CarDescription,
                           StockType = (stockTypes == null) ? null : new
                           {
                               StockTypeID = stockTypes.StockTypeID,
                               StockName = stockTypes.StockName
                           },
                           IsActive = cars.IsActive,
                           IsCab = cars.IsCab,
                           Unit = (carUnit == null) ? null : new
                           {
                               Id = carUnit.UnitId,
                               Name = carUnit.Unit.UnitName
                           },
                           Attributes = 
                              from attribute in context.Attributes
                              .Where(attr => attr.AttributeId==carAttributes.AttributeId).DefaultIfEmpty()
                              .GroupBy(at => at.AttributeId)
                              select attribute
                       };