c# - Converting Flat data to hierarchical -

i getting flat data in c# application list. sample data google drive spreadsheet

i want data converted hierarchical structure. have created json representation of same here

the final structure expecting here

i have created data list in c#. want list converted c# collection object. please give me pointers on easiest way so. [this console application code]

using system; using system.collections.generic; using system.linq; using system.text;  namespace consoleapplication1 { class program {      public class marklist     {      public string student_name { set; get; }     public string frequency  { set; get; }     public string major  { set; get; }     public string subject_category   { set; get; }     public string subject_subcategory { set; get; }      public int spring_mark   { set; get; }     public int autumn_mark   { set; get; }     public int summer_mark { set; get; }            public marklist() { }          public marklist(string student_name,string frequency,string major,string        subject_category,string subject_subcategory,string spring_mark,string autumn_mark,string summer_mark)         {               student_name =student_name;              frequency   =frequency;               major  =major;                subject_category  =subject_category;               subject_subcategory   =subject_subcategory;             spring_mark  =spring_mark;             autumn_mark  =autumn_mark;             summer_mark =summer_mark;          }      }      static void main(string[] args)     {      list<marklist> marklists = new list<marklist>();          marklists.add(new marklist(){student_name="nimalan",frequency="monthly",major="science",subject_category="physics",subject_subcategory="atomic",spring_mark=100,autumn_mark=95,summer_mark=75});         marklists.add(new marklist(){student_name="nimalan",frequency="monthly",major="science", subject_category="physics",subject_subcategory="nuclear",spring_mark=95, autumn_mark=75,summer_mark=100});         marklists.add(new marklist(){student_name="nimalan",frequency="monthly",major="science", subject_category="physics",subject_subcategory="electronics",spring_mark=75, autumn_mark=95,summer_mark=100});         marklists.add(new marklist(){student_name="nimalan",frequency="monthly",major="language", subject_category="tamil",subject_subcategory="literature",spring_mark=80, autumn_mark=90,summer_mark=70});         marklists.add(new marklist(){student_name="nimalan",frequency="monthly",major="commerce" subject_category="retail_data",subject_subcategory="big_data_analytics",spring_mark=90, autumn_mark=80,summer_mark=70});          marklists.add(new marklist(){student_name="nimalan",frequency="weekly",major="science",subject_category="physics",subject_subcategory="atomic",spring_mark=100,autumn_mark=95,summer_mark=75});         marklists.add(new marklist(){student_name="nimalan",frequency="weekly",major="science", subject_category="physics",subject_subcategory="nuclear",spring_mark=95, autumn_mark=75,summer_mark=100});         marklists.add(new marklist(){student_name="nimalan",frequency="weekly",major="science", subject_category="physics",subject_subcategory="electronics",spring_mark=75, autumn_mark=95,summer_mark=100});         marklists.add(new marklist(){student_name="nimalan",frequency="weekly",major="language", subject_category="tamil",subject_subcategory="literature",spring_mark=80, autumn_mark=90,summer_mark=70});         marklists.add(new marklist(){student_name="nimalan",frequency="weekly",major="commerce" subject_category="retail_data",subject_subcategory="big_data_analytics",spring_mark=90, autumn_mark=80,summer_mark=70});          marklists.add(new marklist(){student_name="starnimalan",frequency="monthly",major="science",subject_category="physics",subject_subcategory="atomic",spring_mark=100,autumn_mark=95,summer_mark=75});         marklists.add(new marklist(){student_name="starnimalan",frequency="monthly",major="science", subject_category="physics",subject_subcategory="nuclear",spring_mark=95, autumn_mark=75,summer_mark=100});         marklists.add(new marklist(){student_name="starnimalan",frequency="monthly",major="science", subject_category="physics",subject_subcategory="electronics",spring_mark=75, autumn_mark=95,summer_mark=100});         marklists.add(new marklist(){student_name="starnimalan",frequency="monthly",major="language", subject_category="tamil",subject_subcategory="literature",spring_mark=80, autumn_mark=90,summer_mark=70});         marklists.add(new marklist(){student_name="starnimalan",frequency="monthly",major="commerce" subject_category="retail_data",subject_subcategory="big_data_analytics",spring_mark=90, autumn_mark=80,summer_mark=70});      } } } 

use class created json data using jsonc# http://json2csharp.com/#

public class mark { public string markname { get; set; } public int mark { get; set; } }  public class subjectsubcategory { public string name { get; set; } public list<mark> marks { get; set; } }  public class subjectcategory { public string name { get; set; } public list<subjectsubcategory> subject_subcategory { get; set; } }   public class major { public string name { get; set; } public list<subjectcategory> subject_category { get; set; }  }   public class frequency  { public string name { get; set; } public list<major> major { get; set; }  }  public class product { public string studentname { get; set; }  public list<frequency> frequency { get; set; }  }  public class rootobject { public list<product> product { get; set; } }