MentorGroup

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

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

            string attendancies = Console.ReadLine();
            while (!attendancies.Equals("end of dates"))
            {
                string[] nameAndDates;
                if (attendancies.Contains(" "))
                {
                    nameAndDates = attendancies.Split(' ').ToArray();
                }
                else
                {
                    students.Add(attendancies, new Student());
                    attendancies = Console.ReadLine();
                    continue;
                }

                string studentName = nameAndDates[0];

                if (nameAndDates[1].Contains(","))
                {
                    List<DateTime> dates = new List<DateTime>();

                    string[] allDatesAttended = nameAndDates[1].Split(',');

                    foreach (string date in allDatesAttended)
                    {
                        DateTime currentDate = DateTime.ParseExact(date, "dd/MM/yyyy", CultureInfo.InvariantCulture);

                        dates.Add(currentDate);
                    }

                    if (!students.ContainsKey(studentName))
                    {
                        students.Add(studentName, new Student());
                    }

                    if (students[studentName].Attendancies == null)
                    {
                        students[studentName].Attendancies = new List<DateTime>();
                    }
                    students[studentName].Attendancies.AddRange(dates);
                }
                else
                {
                    string dateAttended = nameAndDates[1];

                    if (!students.ContainsKey(studentName))
                    {
                        students.Add(studentName, new Student());
                    }

                    if (students[studentName].Attendancies == null)
                    {
                        students[studentName].Attendancies = new List<DateTime>();
                    }
                    students[studentName].Attendancies.Add(DateTime.ParseExact(dateAttended, "dd/MM/yyyy", CultureInfo.InvariantCulture));
                }

                attendancies = Console.ReadLine();
            }

            string comments = Console.ReadLine();
            while (!comments.Equals("end of comments"))
            {
                string[] commentsInfo = comments.Split('-').ToArray();

                string fromStudent = commentsInfo[0];
                string studentComment = commentsInfo[1];

                if (!students.ContainsKey(fromStudent) || students[fromStudent].Attendancies == null)
                {
                    comments = Console.ReadLine();
                    continue;
                }

                if (students[fromStudent].Comments == null)
                {
                    students[fromStudent].Comments = new List<string>();
                }
                students[fromStudent].Comments.Add(studentComment);

                comments = Console.ReadLine();
            }

            foreach (KeyValuePair<string, Student> student in students)
            {
                Console.WriteLine("{0}", student.Key);
                Console.WriteLine("Comments:");

                if (student.Value.Comments != null)
                {
                    foreach (string comment in student.Value.Comments)
                    {
                        Console.WriteLine("- {0}", comment);
                    }
                }

                Console.WriteLine("Dates attended:");

                if (student.Value.Attendancies != null)
                {
                    foreach (DateTime attendancy in student.Value.Attendancies.OrderBy(x => x.Date))
                    {
                        Console.WriteLine("-- {0}", attendancy.ToString("dd/MM/yyyy"));
                    }
                }

            }
        }
    }

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

        public List<DateTime> Attendancies { get; set; }
    }
}