C#基础--线程之Task

Task 是.NetFramework3.0出现的，Task里面的线程是来自于线程池

一、Task

1. 开启一个线程

Task 构造函数

传入一个无参数的 Action 委托作为参数

C# 复制代码

Task task = new Task(() =>
                     {
                         this.DoSomethingLong("btntask_Click1");
                     });
task.Start();

Run() 静态方法

C# 复制代码

//Run 为静态方法
Task.Run(() =>
         {
             this.DoSomethingLong("btntask_Click2");
         });

TaskFactory 工厂

C# 复制代码

TaskFactory taskFactory = new TaskFactory();
taskFactory.StartNew(() =>
                     {
                         this.DoSomethingLong("btntask_Click3");
                     });

C# 复制代码

TaskFactory taskFactory = Task.Factory;
taskFactory.StartNew(() =>
                     {
                         this.DoSomethingLong("btntask_Click3");
                     });

Task.Delay 延迟执行

Task.Delay 出现于4.5版本

Thread.Sleep() 是阻塞的，而 Delay 是非阻塞的；如果Sleep 和Delay 平级，则会因Sleep造成阻塞（卡界面）

ContinueWith 类似于回调

C# 复制代码

Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();

//任务在2000ms=2s 以后执行
Task task = Task.Delay(2000).ContinueWith(t =>  
                                          {
                                              Console.WriteLine($"之前花费时间：{stopwatch.ElapsedMilliseconds}");
                                              Console.WriteLine("回调已完成");
                                              Thread.Sleep(2000);
                                              Console.WriteLine($"之后花费时间：{stopwatch.ElapsedMilliseconds}");
                                              stopwatch.Stop();
                                          });

2. 等待任务

2.1 WaitAny

阻塞式，当前线程会等待任意任务结束，然后才能执行后续语句

C# 复制代码

List<Task> tasksList = new List<Task>();

TaskFactory taskFactory = new TaskFactory();

tasksList.Add(taskFactory.StartNew(() => { this.Coding("杰克", "系统管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("流光易逝", "部门管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("偏执", "客户管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("清茶", "接口管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("秋陌", "写Api"); }));

//如果有一个同学完成了某一个模块，老师就需要准备环境！
//等待某一个线程执行完毕以后 继续往后执行
Task.WaitAny(tasksList.ToArray());
Console.WriteLine("Richard老师开始准备环境部署项目！");

2.2 WaitAll

阻塞式，当前线程会等待所有任务结束，然后才能执行后续语句

C# 复制代码

List<Task> tasksList = new List<Task>();

TaskFactory taskFactory = new TaskFactory();

tasksList.Add(taskFactory.StartNew(() => { this.Coding("杰克", "系统管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("流光易逝", "部门管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("偏执", "客户管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("清茶", "接口管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("秋陌", "写Api"); }));

//Richard老师要等待大家都完成了以后，开始给点评！
Task.WaitAll(tasksList.ToArray()); //阻塞主线程
Console.WriteLine("5个模块均已完成，Richard老师点评！");

2.3 WhenAny

非阻塞式，当前线程会返回一个新的任务，在该任务中等待任意任务结束，因此当前线程不会阻塞

C# 复制代码

static int TaskMethod(string name, int seconds)
{
    Console.WriteLine("Task {0} 运行在线程 {1} 上。是否是线程池线程： {2}",
    name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);
    Thread.Sleep(TimeSpan.FromSeconds(seconds));
    return 42 * seconds;
}

var tasks = new List<Task<int>>();
for (int i = 1; i < 4; i++)
{
    int counter = i;
    var task = new Task<int>(() => TaskMethod(string.Format("Task {0}", counter), counter));
    tasks.Add(task);
    task.Start();
}
 
while (tasks.Count > 0)
{
    var completedTask = Task.WhenAny(tasks).Result;//这里的Result是指代Task<int>!
    tasks.Remove(completedTask);
    Console.WriteLine("A task has been completed with result {0}.", completedTask.Result);
}

2.4 WhenAll

非阻塞式，当前线程会返回一个新的任务，在该任务中等待所有任务结束，因此当前线程不会阻塞

C# 复制代码

static int TaskMethod(string name, int seconds)
{
    Console.WriteLine("Task {0} 运行在线程 {1} 上。是否是线程池线程： {2}",
    name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);
    Thread.Sleep(TimeSpan.FromSeconds(seconds));
    return 42 * seconds;
}

var firstTask = new Task<int>(() => TaskMethod("First Task", 3));
var secondTask = new Task<int>(() => TaskMethod("Second Task", 2));
var whenAllTask = Task.WhenAll(firstTask, secondTask);
whenAllTask.ContinueWith(t =>Console.WriteLine("The first answer is {0}, the second is {1}", t.Result[0], t.Result[1])
	, TaskContinuationOptions.OnlyOnRanToCompletion
);
 
firstTask.Start();
secondTask.Start();