Question

我有一个看起来像这样的表：

FruitID | FruitDate | FruitType
  23    |  10/20/14 |   3
  32    |  10/12/14 |   3
  39    |  09/23/14 |   3

有很多FruitTypes，我想提取一个包含最后两个Fruit的对象模型列表，例如{FruitID : 23, Date: 10/20}, {FruitID : 32, Date: 10/12}

这就是我所拥有的：

var Output = (from f in MyDC.Fruits
              where ... some condition
              orderby f.FruitDate descending
              group f by f.FruitType in FruitGroups
              select.... new FruitModel()
              {
                   FruitID = ...
                   FruitDate = ...
                   FruitType = ...

              }).ToList();

我遇到最新问题2.如何找回每个FruitType的最后2个列表？

感谢。

Answer 1

var Output = (from f in MyDC.Fruits
              where ... some condition
              orderby f.FruitDate descending
              group f by f.FruitType in FruitGroups
              select.... new FruitModel()
              {
                   FruitID = ...
                   FruitDate = ...
                   FruitType = ...

              }).Take(2).ToList();

后续编辑

添加了缺少的from子句;这是查询：

var Output = (from f in MyDC.Fruits
              where ... some condition
              orderby f.FruitDate descending
              group f by f.FruitType in FruitGroups
              from t in FruitGroups
              select new FruitModel()
              {
                   FruitID = t.FruitID,
                   FruitDate = t.FruitDate
                   FruitType = t.FruitType

              }).Take(2).ToList();

Answer 2

试试这个： -

var query = from fruit in fruitsData
                        group fruit by fruit.FruitType into g
                        select new
                        {
                            FruitType = g.Key,
                            Fruits = g.OrderByDescending(x => x.FruitDate).Take(2)
                        };

工作Fiddle。

通过降序查询组的前两个元素

2 个答案: