C# linq 实现Rank Over Partition by

public class TData

    {

       public int Id { get; set; }

       public string StuName { get; set; }

       public string ClsName { get; set; }

       public decimal Score { get; set; }

    }

 

 

   public class ToolTest

    {

        [Fact]

       public void Test()

        {

           var list = new List<TData>

            {

               new TData() { Id = 1, StuName = "zhangsan", ClsName = "1", Score = 70 },

               new TData() { Id = 2, StuName = "lisi", ClsName = "1", Score = 80 },

               new TData() { Id = 3, StuName = "wangwu", ClsName = "1", Score = 90 },

               new TData() { Id = 4, StuName = "liaoliu", ClsName = "1", Score = 100 },

               new TData() { Id = 5, StuName = "zhangsan", ClsName = "2", Score = 90 },

               new TData() { Id = 6, StuName = "lisi", ClsName = "2", Score = 40 },

               new TData() { Id = 7, StuName = "wangwu", ClsName = "2", Score = 50 },

               new TData() { Id = 8, StuName = "liaoliu", ClsName = "2", Score = 60 },

            };

 

           //var g = list.GroupBy(g => g.ClsName);

 

           var resut1 = list.GroupBy(g => g.ClsName).Select(s => s.Select(s => s.Score).Max());

 

           var resut2 = list.GroupBy(g => g.ClsName).Select(s => s.OrderByDescending(o => o.Score).FirstOrDefault());

 

        }

    }

 

有个需求，例如：对学生分数排名，且并列排名

FinalAchievement（分数）	Ranking排名
98分	1
97分	2
97分	2
96分	4
96分	4

sql中是： select  Rank Over (order by FinalAchievement desc ) as rank   from datas;

var query = from s in datas
                    orderby s.FinalAchievement descending
                    select new
                    {
                        Name = s.StudentName,
                        Ranking = (from o in datas
                                where float.Parse(o.FinalAchievement) > float.Parse(s.FinalAchievement)
                                select o).Count() + 1
                    };