Main.cs

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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
 
            void Calculate(Result res, String thread)
            {
                while (res.Add < 1000)
                {
                    lock (res)
                    {
                        if (res.Add < 1000)
                        {
                            Console.WriteLine($"{thread}({Thread.CurrentThread.ManagedThreadId}): {res.Add}");
                            res.Answer += (++res.Add);
                        }
                    }
                    Thread.Sleep(10);
                }
            };
            var Res = new Result();
            var workers = new List<Task>();
            for(var i =  0; i < 10; i++)
            {
                workers.Add(Task.Factory.StartNew((name) => Calculate(Res, $"C{name}"), i));
            }
            Task.WaitAll(workers.ToArray());
            Console.Write($"Finish {Res.Answer}");
            Console.ReadKey();
        }
        class Result
        {
            public int Answer = 0;
            public int Add = 0;
        }

    }
}