RoliTheCoder

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace RoliTheCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Event> allEvents = new List<Event>();

            string inputLine = Console.ReadLine();
            while (!inputLine.Equals("Time for Code"))
            {
                bool inputIsValid = CheckIfTheInputLineIsValid(inputLine.Trim());

                if (!inputIsValid)
                {
                    inputLine = Console.ReadLine();
                    continue;
                }

                string[] eventInfo = inputLine.Trim().
                    Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToArray();

                int eventID = int.Parse(eventInfo[0]);
                string eventName = eventInfo[1].TrimStart('#');
                List<string> participants = new List<string>();
                participants = FillTheParticipantsIntoTheList(participants, eventInfo);

                if (allEvents.Any(i => i.ID == eventID))
                {
                    Event excistingEvent = allEvents.First(i => i.ID == eventID);

                    if (!excistingEvent.EventName.Equals(eventName))
                    {
                        inputLine = Console.ReadLine();
                        continue;
                    }
                    excistingEvent.EventParticipants.AddRange(participants);
                    excistingEvent.EventParticipants = excistingEvent.EventParticipants.Distinct().ToList();

                    inputLine = Console.ReadLine();
                    continue;
                }

                Event eventToAdd = new Event();
                eventToAdd.ID = eventID;
                eventToAdd.EventName = eventName;
                eventToAdd.EventParticipants.AddRange(participants);

                allEvents.Add(eventToAdd);

                inputLine = Console.ReadLine();
            }

            PrintResult(allEvents);
        }

        private static void PrintResult(List<Event> allEvents)
        {
            foreach (Event currEvent in allEvents.
                                        OrderByDescending(x => x.EventParticipants.Count).
                                        ThenBy(n => n.EventName))
            {
                Console.WriteLine($"{currEvent.EventName} - {currEvent.EventParticipants.Count}");

                foreach (string participant in currEvent.EventParticipants.OrderBy(x => x))
                {
                    Console.WriteLine(participant);
                }
            }
        }

        private static List<string> FillTheParticipantsIntoTheList(List<string> participants, string[] eventInfo)
        {
            for (int currParticipant = 2; currParticipant < eventInfo.Length; currParticipant++)
            {
                participants.Add(eventInfo[currParticipant]);
            }

            return participants;
        }

        private static bool CheckIfTheInputLineIsValid(string inputLine)
        {
            Regex checker = new Regex(@"^([0-9]+\s+#\w+(\s+@\w+)*)");

            string match = checker.Match(inputLine).Groups[1].ToString();

            return inputLine.Length == match.Length;
        }
    }

    class Event
    {
        public Event()
        {
            EventParticipants = new List<string>();
        }

        public int ID { get; set; }

        public string EventName { get; set; }

        public List<string> EventParticipants { get; set; }
    }
}