MentorGroup

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;

namespace OtherCode
{
    class Program
    {
        static void Main(string[] args)
        {
            SortedDictionary<string, Student> students = new SortedDictionary<string, Student>();

            string input = Console.ReadLine();

            while (input != "end of dates")
            {
                string[] arguments = input.Split().ToArray();

                if (arguments.Length > 1)
                {
                    DateTime[] dates = arguments[1].Split(',').Select(e => DateTime.ParseExact(e, "dd/MM/yyyy", CultureInfo.InvariantCulture)).ToArray();

                    if (!students.ContainsKey(arguments[0]))
                    {
                        Student student = new Student(arguments[0]);
                        foreach (var date in dates)
                        {
                            student.AttendanceDate.Add(date);
                        }
                        students.Add(arguments[0], student);
                    }
                    else
                    {
                        foreach (var date in dates)
                        {
                            students[arguments[0]].AttendanceDate.Add(date);
                        }
                    }
                }
                else
                {
                    if (!students.ContainsKey(arguments[0]))
                    {
                        students.Add(arguments[0], new Student(arguments[0]));
                    }
                }


                input = Console.ReadLine();
            }

            input = Console.ReadLine();

            while (input != "end of comments")
            {
                string[] comments = input.Split('-').ToArray();

                if (students.ContainsKey(comments[0]))
                {
                    students[comments[0]].Comments.Add(comments[1]);
                }

                input = Console.ReadLine();
            }

            foreach (var student in students)
            {
                Console.WriteLine(student.Key);
                Console.WriteLine("Comments:");

                foreach (var comment in student.Value.Comments)
                {
                    Console.WriteLine($"- {comment}");
                }
                Console.WriteLine("Dates attended:");
                foreach (var date in student.Value.AttendanceDate.OrderBy(x => x))
                {
                    Console.WriteLine($"-- {date.ToString("dd/MM/yyyy")}");
                }

            }
        }
        class Student
        {
            public List<string> Comments { get; set; }
            public List<DateTime> AttendanceDate { get; set; }
            public string Name { get; set; }

            public Student(string name)
            {
                this.Comments = new List<string>();
                this.AttendanceDate = new List<DateTime>();
                this.Name = name;
            }
        }
    }
}