C#基礎(chǔ)–線程之Task

Task 是.NetFramework3.0出現(xiàn)的，Task里面的線程是來(lái)自于線程池

一、Task

1. 開(kāi)啟一個(gè)線程

Task 構(gòu)造函數(shù)

傳入一個(gè)無(wú)參數(shù)的 Action 委托作為參數(shù)

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

Run() 靜態(tài)方法

//Run 為靜態(tài)方法
Task.Run(() =>
         {
             this.DoSomethingLong("btntask_Click2");
         });

TaskFactory 工廠

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

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

Task.Delay 延遲執(zhí)行

Task.Delay 出現(xiàn)于4.5版本

Thread.Sleep() 是阻塞的，而 Delay 是非阻塞的；如果Sleep 和Delay 平級(jí)，則會(huì)因Sleep造成阻塞（卡界面）

ContinueWith 類(lèi)似于回調(diào)

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

//任務(wù)在2000ms=2s 以后執(zhí)行
Task task = Task.Delay(2000).ContinueWith(t =>  
                                          {
                                              Console.WriteLine($"之前花費(fèi)時(shí)間：{stopwatch.ElapsedMilliseconds}");
                                              Console.WriteLine("回調(diào)已完成");
                                              Thread.Sleep(2000);
                                              Console.WriteLine($"之后花費(fèi)時(shí)間：{stopwatch.ElapsedMilliseconds}");
                                              stopwatch.Stop();
                                          });

2. 等待任務(wù)

2.1 WaitAny

阻塞式，當(dāng)前線程會(huì)等待任意任務(wù)結(jié)束，然后才能執(zhí)行后續(xù)語(yǔ)句

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

TaskFactory taskFactory = new TaskFactory();

tasksList.Add(taskFactory.StartNew(() => { this.Coding("杰克", "系統(tǒng)管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("流光易逝", "部門(mén)管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("偏執(zhí)", "客戶(hù)管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("清茶", "接口管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("秋陌", "寫(xiě)Api"); }));

//如果有一個(gè)同學(xué)完成了某一個(gè)模塊，老師就需要準(zhǔn)備環(huán)境！
//等待某一個(gè)線程執(zhí)行完畢以后 繼續(xù)往后執(zhí)行
Task.WaitAny(tasksList.ToArray());
Console.WriteLine("Richard老師開(kāi)始準(zhǔn)備環(huán)境部署項(xiàng)目！");

2.2 WaitAll

阻塞式，當(dāng)前線程會(huì)等待所有任務(wù)結(jié)束，然后才能執(zhí)行后續(xù)語(yǔ)句

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

TaskFactory taskFactory = new TaskFactory();

tasksList.Add(taskFactory.StartNew(() => { this.Coding("杰克", "系統(tǒng)管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("流光易逝", "部門(mén)管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("偏執(zhí)", "客戶(hù)管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("清茶", "接口管理"); }));
tasksList.Add(taskFactory.StartNew(() => { this.Coding("秋陌", "寫(xiě)Api"); }));

//Richard老師要等待大家都完成了以后，開(kāi)始給點(diǎn)評(píng)！
Task.WaitAll(tasksList.ToArray()); //阻塞主線程
Console.WriteLine("5個(gè)模塊均已完成，Richard老師點(diǎn)評(píng)！");

2.3 WhenAny

非阻塞式，當(dāng)前線程會(huì)返回一個(gè)新的任務(wù)，在該任務(wù)中等待任意任務(wù)結(jié)束，因此當(dāng)前線程不會(huì)阻塞

static int TaskMethod(string name, int seconds)
{
    Console.WriteLine("Task {0} 運(yùn)行在線程 {1} 上。是否是線程池線程： {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;//這里的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，當(dāng)前線程會(huì)返回一個(gè)新的任務(wù)，在該任務(wù)中等待所有任務(wù)結(jié)束，因此當(dāng)前線程不會(huì)阻塞

static int TaskMethod(string name, int seconds)
{
    Console.WriteLine("Task {0} 運(yùn)行在線程 {1} 上。是否是線程池線程： {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();

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