JavaScript's new Promise and Promise.all counterpart in C#

The result starts with:

and then simultaneously:

task 2 waits for task 1, and then run after 4 seconds, so the event fired at the 6nd second.
taks 3 starts at the beginning, and fired at the 6nd second.

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using System; using System.Threading; using System.Threading.Tasks;   namespace TestAsync {     class Program     {         static void Main(string[] args)         {             var task1 = Task.Factory.StartNew(                 () =>                 {                     Thread.Sleep(2000);                     Console.WriteLine("Task 1 done!");                     return 1;                 });             var task2 = Task.Factory.StartNew(              async () =>                 {                     await task1;                     Thread.Sleep(4000);                     Console.WriteLine("Task 2 done!");                     return 2;                 });             var task3 = Task.Factory.StartNew(                 () =>                 {                     Thread.Sleep(6000);                     Console.WriteLine("Task 3 done!");                     return 3;                 });               var aTimer = new System.Timers.Timer();             aTimer.Interval = 100;             aTimer.Elapsed += (source, args) => { Console.Write("."); };             aTimer.AutoReset = true;             aTimer.Enabled = true;               Task.WhenAll(task1, task2, task3).ContinueWith(results =>             {                 aTimer.Enabled = false;                 int result = task1.Result + task2.Result.Result + task3.Result;                 Console.WriteLine($"result: {result}");             });               Console.ReadLine();           }     } }