threads.cs

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

namespace pr2
{
    class Program
    {
        static bool useCountDownEvent = true;

        static void Main(string[] args)
        {
            if (useCountDownEvent)
            {
                Console.WriteLine("Using CountDownEvent:");
                new UsingCountDownEvent();
            }
            else
            {
                Console.WriteLine("Using Join:");
                new UsingJoin();
            }

            Console.ReadKey();
        }
    }
    
    class UsingCountDownEvent
    {
        Thread[] threads = new Thread[9];

        CountdownEvent[] counters = new CountdownEvent[4];

        public UsingCountDownEvent()
        {

            for (int i = 0; i < 4; ++i)
            {
                // 0 - counter for event 4
                // 1 - counter for event 5
                // 2 - counter for event 6
                // 3 - coutner for event 7
                counters[i] = new CountdownEvent(3);
            }

            threads[0] = new Thread(() => event123(1));
            threads[1] = new Thread(() => event123(2));
            threads[2] = new Thread(() => event123(3));

            threads[3] = new Thread(event4);

            threads[4] = new Thread(() => event567(5));
            threads[5] = new Thread(() => event567(6));
            threads[6] = new Thread(() => event567(7));

            threads[7] = new Thread(() => event89(8));
            threads[8] = new Thread(() => event89(9));

            foreach (Thread thread in threads)
            {
                thread.Start();
            }

            foreach (Thread thread in threads)
            {
                if (thread.IsAlive)
                {
                    thread.Join();
                }
            }

            Console.ReadKey();

        }

        void event123(int n)
        {
            Console.WriteLine("Message from event " + n);

            counters[0].Signal();
        }

        void event4()
        {
            counters[0].Wait();

            Console.WriteLine("Message from event 4");

            signal567();
        }

        void event567(int n)
        {
            counters[n - 4].Wait();

            Console.WriteLine("Message from event " + n);
        }

        void event89(int n)
        {
            Console.WriteLine("Message from event " + n);

            signal567();
        }

        void signal567()
        {
            counters[1].Signal();
            counters[2].Signal();
            counters[3].Signal();
        }
    }
    
    class UsingJoin
    {
        Thread[] threads = new Thread[9];

        public UsingJoin()
        {
            threads[0] = new Thread(() => event123(1));
            threads[1] = new Thread(() => event123(2));
            threads[2] = new Thread(() => event123(3));

            threads[3] = new Thread(event4);

            threads[4] = new Thread(() => event567(5));
            threads[5] = new Thread(() => event567(6));
            threads[6] = new Thread(() => event567(7));

            threads[7] = new Thread(() => event89(8));
            threads[8] = new Thread(() => event89(9));

            foreach (Thread thread in threads)
            {
                thread.Start();
            }

            foreach (Thread thread in threads)
            {
                if (thread.IsAlive)
                {
                    thread.Join();
                }
            }
        }

        void event123(int n)
        {
            Console.WriteLine("Message from event " + n);
        }

        void event4()
        {
            threads[0].Join();
            threads[1].Join();
            threads[2].Join();

            Console.WriteLine("Message from event 4");
        }

        void event567(int n)
        {
            threads[3].Join();
            threads[7].Join();
            threads[8].Join();

            Console.WriteLine("Message from event " + n);
        }

        void event89(int n)
        {
            Console.WriteLine("Message from event " + n);
        }
    }
}