Waiting for all tasks but cancel them all the moment one of them fails.

tasks.cs

    [TestClass]
    public class TaskTests
    {
        [TestMethod]
        public async Task Trololo()
        {
            Console.WriteLine("Starting");
            var tokenSource = new CancellationTokenSource();
            var token = tokenSource.Token;
            Task task1 = Task.Run(async () =>
            {
                await Task.Delay(1000, token);
                Console.WriteLine("Finished task 1");
            }, token);
            Task task2 = Task.Run(async () =>
            {
                await Task.Delay(2000, token);
                Console.WriteLine("Task 2 throwing...");
                throw new Exception();
            }, token);
            Task task3 = Task.Run(async () =>
            {
                await Task.Delay(4000, token);
                if (token.IsCancellationRequested)
                {
                    return;
                }

                Console.WriteLine("Finished task 3 (BAD)");
            }, token);

            try
            {
                await WaitAllThrowingAtFirstFail(new[] { task1, task2, task3 });
                Console.WriteLine("Finished all tasks");
            }
            catch
            {
                tokenSource.Cancel();
                Console.WriteLine("One task failed");
            }

            await Task.Delay(6000);
        }

        private async Task WaitAllThrowingAtFirstFail(IEnumerable<Task> tasks)
        {
            List<Task> taskList = tasks.ToList();

            while (taskList.Count > 0)
            {
                Task firstFinishedTask = await Task.WhenAny(taskList);
                if (firstFinishedTask.IsFaulted)
                {
                    throw new Exception();
                }

                taskList.Remove(firstFinishedTask);
                await firstFinishedTask;
            }
        }

        private async Task<IEnumerable<T>> WaitAllThrowingAtFirstFail<T>(IEnumerable<Task<T>> tasks)
        {
            List<Task<T>> taskList = tasks.ToList();
            List<T> results = new List<T>();
            while (taskList.Count > 0)
            {
                Task<T> firstFinishedTask = await Task.WhenAny(taskList);
                if (firstFinishedTask.IsFaulted)
                {
                    throw new Exception();
                }

                taskList.Remove(firstFinishedTask);
                if (firstFinishedTask.IsCompleted)
                {
                    results.Add(firstFinishedTask.Result);
                }
            }

            return results;
        }
        
    }