using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using static System.Console;

​

public class Student

{

    public int ID { get; set; }

    public string Name { get; set; }

    public string Gender { get; set; }

    public string Branch { get; set; }

    public int Age { get; set; }

    public static List<Student> GetAllStudent()

    {

        return new List<Student>()

        {

            new Student { ID = 1001, Name = "Preety", Gender = "Female", Branch = "CSE", Age = 20 },

            new Student { ID = 1002, Name = "Snurag", Gender = "Male", Branch = "ETC", Age = 21  },

            new Student { ID = 1003, Name = "Pranaya", Gender = "Male", Branch = "CSE", Age = 21  },

            new Student { ID = 1004, Name = "Anurag", Gender = "Male", Branch = "CSE", Age = 20  },

            new Student { ID = 1005, Name = "Hina", Gender = "Female", Branch = "ETC", Age = 20 },

            new Student { ID = 1006, Name = "Priyanka", Gender = "Female", Branch = "CSE", Age = 21 },

            new Student { ID = 1007, Name = "santosh", Gender = "Male", Branch = "CSE", Age = 22  },

            new Student { ID = 1008, Name = "Tina", Gender = "Female", Branch = "CSE", Age = 20  },

            new Student { ID = 1009, Name = "Celina", Gender = "Female", Branch = "ETC", Age = 22 },

            new Student { ID = 1010, Name = "Sambit", Gender = "Male",Branch = "ETC", Age = 21 }

        };

    }

}

public class Program

{

    public static void Main()

    {

        var toLookupMultipleKeyMS = Student.GetAllStudent()

                                            .ToLookup(s => new{s.Branch, s.Gender})

                                            .Select(student => new

                                                    {

                                                        Branch = student.Key.Branch,

                                                        Gender = student.Key.Gender,

                                                        Student = student.OrderBy(s => s.Name)

                                                    });

        var toLookupMultipleKeyQS = (from std in Student.GetAllStudent()

                                     select std).ToLookup(s => new{s.Branch, s.Gender})

                                     .Select(student => new

                                             {

                                                 Branch = student.Key.Branch,

                                                 Gender = student.Key.Gender,

                                                 Student = student.OrderBy(s => s.Name)

                                             });

        //It will iterate through each group

        foreach (var group in toLookupMultipleKeyQS)

        {

         WriteLine($"Barnch: {group.Branch} Gender: {group.Gender} No of Students = {group.Student.Count()}");

            //It will iterate through each item of a group

            foreach (var student in group.Student)

            {

                Console.WriteLine($"  ID: {student.ID}, Name: {student.Name}, Age: {student.Age} ");

            }

        }

        ReadLine();

    }

}