using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
namespace AsyncAwait
{
class Program
{
//http://www.cnblogs.com/sheng-jie/p/6471986.html
// 3.3. 什么是前台线程
// 默认情况下，使用Thread.Start()方法创建的线程都是前台线程。前台线程能阻止应用程序的终结，只有所有的前台线程执行完毕，CLR才能关闭应用程序（即卸载承载的应用程序域）。前台线程也属于工作者线程。
//3.4. 什么是后台线程
// 后台线程不会影响应用程序的终结，当所有前台线程执行完毕后，后台线程无论是否执行完毕，都会被终结。一般后台线程用来做些无关紧要的任务（比如邮箱每隔一段时间就去检查下邮件，天气应用每隔一段时间去更新天气）。后台线程也属于工作者线程。
static void Main(string[] args)
{
//C# async关键字用来指定某个方法、Lambda表达式或匿名方法自动以异步的方式来调用。
Console.WriteLine("主线程启动，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
var task = GetLengthAsync();
Console.WriteLine("回到主线程，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
Console.WriteLine("线程【" + Thread.CurrentThread.ManagedThreadId + "】睡眠5s:");
Thread.Sleep(5000); //将主线程睡眠5s
var timer = new Stopwatch();
timer.Start(); //开始计算时间
Console.WriteLine("task的返回值是" + task.Result);
timer.Stop(); //结束点，另外StopWatch还有Reset方法，可以重置。
Console.WriteLine("等待了：" + timer.Elapsed.TotalSeconds + "秒");//显示时间
Console.WriteLine("主线程结束，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
//Console.WriteLine("主线程开始！");
//ForeBackGround();
//ThreadPoolTest();
Console.ReadKey();
}
private static async Task<int> GetLengthAsync()
{
Console.WriteLine("GetLengthAsync()开始执行，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
var str = await GetStringAsync();
Console.WriteLine("GetLengthAsync()执行完毕，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
return str.Length;
}
private static Task<string> GetStringAsync()
{
Console.WriteLine("GetStringAsync()开始执行，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
return Task.Run(() =>
{
Console.WriteLine("异步任务开始执行，当前线程为：" + Thread.CurrentThread.ManagedThreadId);
Console.WriteLine("线程【" + Thread.CurrentThread.ManagedThreadId + "】睡眠10s");
Thread.Sleep(10000); //将异步任务线程睡眠10s
return "GetStringAsync()执行完毕";
});
}
public static void TaskDemo2()
{
Console.WriteLine("主线程ID：" + Thread.CurrentThread.ManagedThreadId);
Task.Run(() => Console.WriteLine("Task对应线程ID：" + Thread.CurrentThread.ManagedThreadId));
Console.ReadLine();
}
public static void TaskDemo()
{
Console.WriteLine("主线程ID：" + Thread.CurrentThread.ManagedThreadId);
Task.Factory.StartNew(() => Console.WriteLine("Task对应线程ID：" + Thread.CurrentThread.ManagedThreadId));
Console.ReadKey();
}
/// <summary>
/// ThreadPool（线程池）
/// </summary>
public static void ThreadPoolTest()
{
WaitCallback workItem = state => Console.WriteLine("当前线程Id为：" + Thread.CurrentThread.ManagedThreadId);
for (int i = 0; i < 10; i++)
{
ThreadPool.QueueUserWorkItem(workItem);
}
}
/// <summary>
/// 前台线程、后台线程
/// </summary>
private static void ForeBackGround()
{
//创建前台工作线程
Thread t1 = new Thread(Task1);
t1.Start();
//创建后台工作线程
Thread t2 = new Thread(new ParameterizedThreadStart(Task2));
t2.IsBackground = true; //设置为后台线程
t2.Start("传参");
}
private static void Task1()
{
Thread.Sleep(1000); //模拟耗时操作，睡眠1S
Console.WriteLine("前台线程被调用！");
}
private static void Task2(object data)
{
Thread.Sleep(2000); //模拟耗时操作，睡眠2S
Console.WriteLine("后台线程被调用！" + data);
}
}
}