Task_async.cs

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

class Program
{
  static void Main(string[] args)
  {
    DateTime start = DateTime.Now;
    var test1 = Test1(12345);
    IEnumerable<int> counter1 = Enumerable.Range(0, 10);
    foreach(int i in counter1)
    {
      Console.WriteLine(i);
      System.Threading.Thread.Sleep(20);
    }
    Console.WriteLine(test1.Result);
    Console.WriteLine(DateTime.Now - start);
  }
  
  static async Task<string> Test1(int x)
  {
    await Task.Delay(10);
    await Task.Run(() =>
    {
      var counter2 = Enumerable.Range(0, 10);
      foreach(int i in counter2)
      {
        Console.WriteLine("---");
        System.Threading.Thread.Sleep(20);
      }
    });
    return x.ToString();
  }
}