Linq order by group by and order by each group

Question

I have an object that looks something like this   public class Student       public string Name   get  set         public int Grade   get  set        I would like to create the following query  group grades by student name  order each student group by grades  and order groups by max grade in each group   So it will look like this    A 100 A 80 B 80 B 50 B 40 C 70 C 30   I created the following query   StudentsGrades GroupBy student   gt  student Name       OrderBy studentGradesGroup   gt  studentGradesGroup Max student   gt  student Grade      But that returns IEnumerable IGrouping  and I have no way to sort the list inside  unless I do that in another foreach query and add the results to a different list using AddRange   Is there a prettier way to do that

User · Answer

try this     public class Student                public int Grade   get  set            public string Name   get  set            public override string ToString                         return string Format  Name 0    Grade 1    Name  Grade                    class Program       static void Main string   args               List lt Student gt  listStudents   new List lt Student gt           listStudents Add new Student     Grade   10  Name    Pedro            listStudents Add new Student     Grade   10  Name    Luana            listStudents Add new Student     Grade   10  Name    Maria            listStudents Add new Student     Grade   11  Name    Mario            listStudents Add new Student     Grade   15  Name    Mario            listStudents Add new Student     Grade   10  Name    Bruno            listStudents Add new Student     Grade   10  Name    Luana            listStudents Add new Student     Grade   11  Name    Luana            listStudents Add new Student     Grade   22  Name    Maria            listStudents Add new Student     Grade   55  Name    Bruno            listStudents Add new Student     Grade   77  Name    Maria            listStudents Add new Student     Grade   66  Name    Maria            listStudents Add new Student     Grade   88  Name    Bruno            listStudents Add new Student     Grade   42  Name    Pedro            listStudents Add new Student     Grade   33  Name    Bruno            listStudents Add new Student     Grade   33  Name    Luciana            listStudents Add new Student     Grade   17  Name    Maria            listStudents Add new Student     Grade   25  Name    Luana            listStudents Add new Student     Grade   25  Name    Pedro             listStudents GroupBy g   gt  g Name  OrderBy g   gt  g Key  SelectMany g   gt  g OrderByDescending x   gt  x Grade   ToList   ForEach x   gt  Console WriteLine x ToString

User · Answer

I think you want an additional projection that maps each group to a sorted-version of the group    Select group   gt  group OrderByDescending student   gt  student Grade       It also appears like you might want another flattening operation after that which will give you a sequence of students instead of a sequence of groups    SelectMany group   gt  group    You can always collapse both into a single SelectMany call that does the projection and flattening together     EDIT  As Jon Skeet points out  there are certain inefficiencies in the overall query  the information gained from sorting each group is not being used in the ordering of the groups themselves  By moving the sorting of each group to come before the ordering of the groups themselves  the Max query can be dodged into a simpler First query

User · Answer

Sure   var query   grades GroupBy student   gt  student Name                     Select group   gt                           new   Name   group Key                                Students   group OrderByDescending x   gt  x Grade                        OrderBy group   gt  group Students First   Grade     Note that you can get away with just taking the first grade within each group after ordering  because you already know the first entry will be have the highest grade   Then you could display them with   foreach  var group in query        Console WriteLine  Group   0    group Name       foreach  var student in group Students                Console WriteLine     0    student Grade

User · Answer

The way to do it without projection   StudentsGrades OrderBy student   gt  student Name   ThenBy student   gt  student Grade

User · Answer

Alternatively you can do  like this         var  items   from a in StudentsGrades                   group a by a Name        foreach  var  itemGroup in  items                 foreach  var  item in  itemGroup OrderBy a  gt a grade                        ------------------------            --------------------------

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