AbnormalDelay.cs

using System;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        private static Task _sharedTask;

        static void Main(string[] args)
        {
            var tcs = new TaskCompletionSource<bool>();
            _sharedTask = tcs.Task;

            Task.Run(Thread1);
            Thread.Sleep(1000); // Wait for the task to start

            Task.Run(Thread2);
            Thread.Sleep(1000); // Wait for the task to start

            Task.Run(() => Thread3());
            Thread.Sleep(1000); // Wait for the task to start

            Console.WriteLine("Shared task completed at {0}", DateTime.Now.ToLongTimeString());
            tcs.SetResult(true);

            Console.ReadLine();
        }

        private static async Task Thread1()
        {
            await _sharedTask;

            // Simulate some work
            Thread.Sleep(10000);

            Console.WriteLine("Thread1 completed at {0}", DateTime.Now.ToLongTimeString());
        }

        private static async Task Thread2()
        {
            await _sharedTask;

            // No additional work, this task is expected to complete quickly

            Console.WriteLine("Thread2 completed at {0}", DateTime.Now.ToLongTimeString());
        }

        private static void Thread3()
        {
            _sharedTask.ContinueWith(_ =>
            {
                // No additional work, this task is expected to complete quickly

                Console.WriteLine("Thread3 completed at {0}", DateTime.Now.ToLongTimeString());
            });
        }
    }
}