using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

        public static void Main(string[] args)

        {

            List<RawData> data = new List<RawData>();

​

            RawData r1 = new RawData() { PrimaryColumn = 1, StudentID = 1, StrudentName = "X", CourseName = "Cse1", CourseID = "C1", CourseDuration = 2 };

            data.Add(r1);

​

            RawData r2 = new RawData() { PrimaryColumn = 2, StudentID = 1, StrudentName = "X", CourseName = "Cse2", CourseID = "C2", CourseDuration = 1 };

            data.Add(r2);

​

            RawData r3 = new RawData() { PrimaryColumn = 3, StudentID = 1, StrudentName = "X", CourseName = "Cse3", CourseID = "C3", CourseDuration = 3 };

            data.Add(r3);

​

            RawData r4 = new RawData() { PrimaryColumn = 4, StudentID = 2, StrudentName = "Y", CourseName = "Cse1", CourseID = "C1", CourseDuration = 2 };

            data.Add(r4);

​

            RawData r5 = new RawData() { PrimaryColumn = 5, StudentID = 2, StrudentName = "Y", CourseName = "Cse4", CourseID = "C4", CourseDuration = 5 };

            data.Add(r5);

​

​

            var result = data.GroupBy(x => new { x.StudentID, x.StrudentName }, 

                (key, group) => new Student{ StudentId = key.StudentID, StudentName = key.StrudentName, Courses = GetCourses(group)}).ToList();

            foreach(var item in result)

            {

                Console.WriteLine(item.StudentId);

            }

        }

​

​

        public static List<Course> GetCourses(IEnumerable<RawData> data)

        {

            List<Course> course = new List<Course>();

​

            foreach(var item in data)

            {

                Course c = new Course();

​

                c.CourseDuration = item.CourseDuration;

                c.CourseId = item.CourseID;

                c.CourseName = item.CourseName;

​

                course.Add(c);

            }

​

            return course;

        }

        public class RawData

        {

            public int PrimaryColumn { get; set; }

​

            public int StudentID { get; set; }

​

            public string StrudentName { get; set; }

​

            public string CourseName { get; set; }

​

            public string CourseID { get; set; }

​

            public int CourseDuration { get; set; }

        }

​

        public class Student 

        {

              public int StudentId {get; set;}

              public string StudentName { get; set; }

              public List<Course> Courses {get; set;}

        }    

​

        public class Course 

        {

              public string CourseId {get; set;}

              public string CourseName {get; set;}

              public int CourseDuration {get; set; }

        }

​

}