Task

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Web;

namespace ConsoleApp5
{
    class Program
    {
        static void Main(string[] args)
        {
            MyDownLoadString ds = new MyDownLoadString();
            ds.DoRun();
            Console.ReadKey();
        }
    }
    class MyDownLoadString
    {
        Stopwatch sw = new Stopwatch();
        public void DoRun()
        {
            const int LargeNumber = 6000000;
            sw.Start();
            // Task<int> 保存结果对象，后面t1.Result则是获取结果
            Task<int> t1 = CountCharactersAsync(1, "http://www.microsoft.com");
            Task<int> t2 = CountCharactersAsync(2, "http://www.illustratedcsharp.com");

            //无需等待CountCharactersAsync执行完成
            CountToALargeNumber(1, LargeNumber);
            CountToALargeNumber(2, LargeNumber);
            CountToALargeNumber(3, LargeNumber);
            CountToALargeNumber(4, LargeNumber);

            //t1.Result获取结果
            Console.WriteLine("Chars in Call1:{0}", t1.Result);
            Console.WriteLine("Chars in Call1:{0}", t2.Result);
        }

        private async Task<int> CountCharactersAsync(int id, string uriString)
        {
            WebClient wc = new WebClient();
            Console.WriteLine("Call {0} 下载开始: {1:N0}ms ", id, sw.Elapsed.TotalMilliseconds);
            string result = await wc.DownloadStringTaskAsync(new Uri(uriString));
           // Trace.TraceInformation("Taceing Async Call {0} @time:{1:N0}ms", id, sw.Elapsed.TotalMilliseconds);
            Console.WriteLine("Call {0} 下载结束: {1:N0}ms", id, sw.Elapsed.TotalMilliseconds);
            return result.Length;
        }

        private void CountToALargeNumber(int id, int value)
        {
            for (long i = 0; i < value; i++) ;
            Console.WriteLine("End CountToALargeNumber {0}: {1:N0}ms", id, sw.Elapsed.TotalMilliseconds);
        }
    }
    }

using System;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp3
{
    class Program
    {
        private static UdpClient udpcSend;
        static void Main(string[] args)
        {

            MyDownLoadString ds = new MyDownLoadString();
            ds.DoRun();
            Console.ReadKey();
        }       
    }

    class MyDownLoadString 
    {
        public void DoRun() 
        {
            Console.WriteLine("DoRun开始！！！！！！");
            Task t1 = CountCharactersAsync();
            Console.WriteLine("DoRun结束！！！！！！");
        }

        private async Task CountCharactersAsync()
        {

            List<Task> tasks = new List<Task>();
            tasks.Add(Task.Run(async () => {
                Thread.Sleep(10000);
                Console.WriteLine("比对1");
            }));
            tasks.Add(Task.Run(async () => {
                Thread.Sleep(10);
                Console.WriteLine("比对2");
            }));
            tasks.Add(Task.Run(async () => {              
                Console.WriteLine("比对3");
            }));
            tasks.Add(Task.Run(async () => {
                Thread.Sleep(1000);
                Console.WriteLine("比对4");
            }));
            //await Task.WhenAll(tasks);
            //await Task.WhenAny(tasks);
            // Task.WaitAll(tasks.ToArray());
            //Task.WaitAny(tasks.ToArray());//只要一个执行了就往下
            Console.WriteLine("等待结束！！");
        }
    }
}