c# task添加顺序_C# Task详解
1、Task的优势
ThreadPool相比Thread来说具备了很多优势，但是ThreadPool却又存在一些使用上的不方便。比如：
◆ ThreadPool不支持线程的取消、完成、失败通知等交互性操作；
◆ ThreadPool不支持线程执行的先后次序；
以往，如果开发者要实现上述功能，需要完成很多额外的工作，现在，FCL中提供了一个功能更强大的概念：Task。Task在线程池的基础上进行了优化，并提供了更多的API。在FCL4.0中，如果我们要编写多线程程序，Task显然已经优于传统的方式。
以下是一个简单的任务示例：
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static void Main(string[] args)
{
Task t= new Task(() =>{
Console.WriteLine("任务开始工作……");//模拟工作过程
Thread.Sleep(5000);
});
t.Start();
t.ContinueWith((task)=>{
Console.WriteLine("任务完成，完成时候的状态为：");
Console.WriteLine("IsCanceled={0}\tIsCompleted={1}\tIsFaulted={2}", task.IsCanceled, task.IsCompleted, task.IsFaulted);
});
Console.ReadKey();
}
}
}
View Code
2、Task的用法
2.1、创建任务
(一)无返回值的方式
方式1:
var t1 = new Task(() => TaskMethod("Task 1"));
t1.Start();
Task.WaitAll(t1);//等待所有任务结束
注:任务的状态:
Start之前为:Created
Start之后为:WaitingToRun
方式2:
Task.Run(() => TaskMethod("Task 2"));
方式3:
Task.Factory.StartNew(() => TaskMethod("Task 3")); 直接异步的方法//或者
var t3=Task.Factory.StartNew(() => TaskMethod("Task 3"));
Task.WaitAll(t3);//等待所有任务结束//任务的状态:
Start之前为:Running
Start之后为:Running
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static void Main(string[] args)
{var t1 = new Task(() => TaskMethod("Task 1"));var t2 = new Task(() => TaskMethod("Task 2"));
t2.Start();
t1.Start();
Task.WaitAll(t1, t2);
Task.Run(()=> TaskMethod("Task 3"));
Task.Factory.StartNew(()=> TaskMethod("Task 4"));//标记为长时间运行任务,则任务不会使用线程池,而在单独的线程中运行。
Task.Factory.StartNew(() => TaskMethod("Task 5"), TaskCreationOptions.LongRunning);#region 常规的使用方式Console.WriteLine("主线程执行业务处理.");//创建任务
Task task = new Task(() =>{
Console.WriteLine("使用System.Threading.Tasks.Task执行异步操作.");for (int i = 0; i < 10; i++)
{
Console.WriteLine(i);
}
});//启动任务,并安排到当前任务队列线程中执行任务(System.Threading.Tasks.TaskScheduler)
task.Start();
Console.WriteLine("主线程执行其他处理");
task.Wait();#endregionThread.Sleep(TimeSpan.FromSeconds(1));
Console.ReadLine();
}static void TaskMethod(stringname)
{
Console.WriteLine("Task {0} is running on a thread id {1}. Is thread pool thread: {2}",
name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);
}
}
}
View Code
async/await的实现方式:
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{async static voidAsyncFunction()
{await Task.Delay(1);
Console.WriteLine("使用System.Threading.Tasks.Task执行异步操作.");for (int i = 0; i < 10; i++)
{
Console.WriteLine(string.Format("AsyncFunction:i={0}", i));
}
}public static voidMain()
{
Console.WriteLine("主线程执行业务处理.");
AsyncFunction();
Console.WriteLine("主线程执行其他处理");for (int i = 0; i < 10; i++)
{
Console.WriteLine(string.Format("Main:i={0}", i));
}
Console.ReadLine();
}
}
}
View Code
(二)带返回值的方式
方式4:
Task task = CreateTask("Task 1");
task.Start();int result = task.Result;
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static Task CreateTask(stringname)
{return new Task(() =>TaskMethod(name));
}static void Main(string[] args)
{
TaskMethod("Main Thread Task");
Task task = CreateTask("Task 1");
task.Start();int result =task.Result;
Console.WriteLine("Task 1 Result is: {0}", result);
task= CreateTask("Task 2");//该任务会运行在主线程中
task.RunSynchronously();
result=task.Result;
Console.WriteLine("Task 2 Result is: {0}", result);
task= CreateTask("Task 3");
Console.WriteLine(task.Status);
task.Start();while (!task.IsCompleted)
{
Console.WriteLine(task.Status);
Thread.Sleep(TimeSpan.FromSeconds(0.5));
}
Console.WriteLine(task.Status);
result=task.Result;
Console.WriteLine("Task 3 Result is: {0}", result);#region 常规使用方式
//创建任务
Task getsumtask = new Task(() =>Getsum());//启动任务,并安排到当前任务队列线程中执行任务(System.Threading.Tasks.TaskScheduler)
getsumtask.Start();
Console.WriteLine("主线程执行其他处理");//等待任务的完成执行过程。
getsumtask.Wait();//获得任务的执行结果
Console.WriteLine("任务执行结果：{0}", getsumtask.Result.ToString());#endregion}static int TaskMethod(stringname)
{
Console.WriteLine("Task {0} is running on a thread id {1}. Is thread pool thread: {2}",
name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);
Thread.Sleep(TimeSpan.FromSeconds(2));return 42;
}static intGetsum()
{int sum = 0;
Console.WriteLine("使用Task执行异步操作.");for (int i = 0; i < 100; i++)
{
sum+=i;
}returnsum;
}
}
}
View Code
async/await的实现:
usingSystem;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{public static voidMain()
{var ret1 =AsyncGetsum();
Console.WriteLine("主线程执行其他处理");for (int i = 1; i <= 3; i++)
Console.WriteLine("Call Main()");int result = ret1.Result; //阻塞主线程
Console.WriteLine("任务执行结果：{0}", result);
}async static TaskAsyncGetsum()
{await Task.Delay(1);int sum = 0;
Console.WriteLine("使用Task执行异步操作.");for (int i = 0; i < 100; i++)
{
sum+=i;
}returnsum;
}
}
}
View Code
2.2、组合任务.ContinueWith
简单Demo:
usingSystem;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{public static voidMain()
{//创建一个任务
Task task = new Task(() =>{int sum = 0;
Console.WriteLine("使用Task执行异步操作.");for (int i = 0; i < 100; i++)
{
sum+=i;
}returnsum;
});//启动任务,并安排到当前任务队列线程中执行任务(System.Threading.Tasks.TaskScheduler)
task.Start();
Console.WriteLine("主线程执行其他处理");//任务完成时执行处理。
Task cwt = task.ContinueWith(t =>{
Console.WriteLine("任务完成后的执行结果：{0}", t.Result.ToString());
});
task.Wait();
cwt.Wait();
}
}
}
View Code
任务的串行:
usingSystem;usingSystem.Collections.Concurrent;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static void Main(string[] args)
{
ConcurrentStack stack = new ConcurrentStack();//t1先串行
var t1 = Task.Factory.StartNew(() =>{
stack.Push(1);
stack.Push(2);
});//t2,t3并行执行
var t2 = t1.ContinueWith(t =>{intresult;
stack.TryPop(outresult);
Console.WriteLine("Task t2 result={0},Thread id {1}", result, Thread.CurrentThread.ManagedThreadId);
});//t2,t3并行执行
var t3 = t1.ContinueWith(t =>{intresult;
stack.TryPop(outresult);
Console.WriteLine("Task t3 result={0},Thread id {1}", result, Thread.CurrentThread.ManagedThreadId);
});//等待t2和t3执行完
Task.WaitAll(t2, t3);//t7串行执行
var t4 = Task.Factory.StartNew(() =>{
Console.WriteLine("当前集合元素个数：{0},Thread id {1}", stack.Count, Thread.CurrentThread.ManagedThreadId);
});
t4.Wait();
}
}
}
View Code
子任务:
usingSystem;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{public static voidMain()
{
Task parent = new Task(state =>{
Console.WriteLine(state);string[] result = new string[2];//创建并启动子任务
new Task(() => { result[0] = "我是子任务1。"; }, TaskCreationOptions.AttachedToParent).Start();new Task(() => { result[1] = "我是子任务2。"; }, TaskCreationOptions.AttachedToParent).Start();returnresult;
},"我是父任务，并在我的处理过程中创建多个子任务，所有子任务完成以后我才会结束执行。");//任务处理完成后执行的操作
parent.ContinueWith(t =>{
Array.ForEach(t.Result, r=>Console.WriteLine(r));
});//启动父任务
parent.Start();//等待任务结束 Wait只能等待父线程结束,没办法等到父线程的ContinueWith结束//parent.Wait();
Console.ReadLine();
}
}
}
View Code
动态并行(TaskCreationOptions.AttachedToParent) 父任务等待所有子任务完成后 整个任务才算完成
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classNode
{public Node Left { get; set; }public Node Right { get; set; }public string Text { get; set; }
}classProgram
{staticNode GetNode()
{
Node root= newNode
{
Left= newNode
{
Left= newNode
{
Text= "L-L"},
Right= newNode
{
Text= "L-R"},
Text= "L"},
Right= newNode
{
Left= newNode
{
Text= "R-L"},
Right= newNode
{
Text= "R-R"},
Text= "R"},
Text= "Root"};returnroot;
}static void Main(string[] args)
{
Node root=GetNode();
DisplayTree(root);
}static voidDisplayTree(Node root)
{var task = Task.Factory.StartNew(() =>DisplayNode(root),
CancellationToken.None,
TaskCreationOptions.None,
TaskScheduler.Default);
task.Wait();
}static voidDisplayNode(Node current)
{if (current.Left != null)
Task.Factory.StartNew(()=>DisplayNode(current.Left),
CancellationToken.None,
TaskCreationOptions.AttachedToParent,
TaskScheduler.Default);if (current.Right != null)
Task.Factory.StartNew(()=>DisplayNode(current.Right),
CancellationToken.None,
TaskCreationOptions.AttachedToParent,
TaskScheduler.Default);
Console.WriteLine("当前节点的值为{0};处理的ThreadId={1}", current.Text, Thread.CurrentThread.ManagedThreadId);
}
}
}
View Code
2.3、取消任务 CancellationTokenSource
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{private static int TaskMethod(string name, intseconds, CancellationToken token)
{
Console.WriteLine("Task {0} is running on a thread id {1}. Is thread pool thread: {2}",
name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);for (int i = 0; i < seconds; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(1));if (token.IsCancellationRequested) return -1;
}return 42 *seconds;
}private static void Main(string[] args)
{var cts = newCancellationTokenSource();var longTask = new Task(() => TaskMethod("Task 1", 10, cts.Token), cts.Token);
Console.WriteLine(longTask.Status);
cts.Cancel();
Console.WriteLine(longTask.Status);
Console.WriteLine("First task has been cancelled before execution");
cts= newCancellationTokenSource();
longTask= new Task(() => TaskMethod("Task 2", 10, cts.Token), cts.Token);
longTask.Start();for (int i = 0; i < 5; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(0.5));
Console.WriteLine(longTask.Status);
}
cts.Cancel();for (int i = 0; i < 5; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(0.5));
Console.WriteLine(longTask.Status);
}
Console.WriteLine("A task has been completed with result {0}.", longTask.Result);
}
}
}
View Code
2.4、处理任务中的异常
单个任务:
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static int TaskMethod(string name, intseconds)
{
Console.WriteLine("Task {0} is running on a thread id {1}. Is thread pool thread: {2}",
name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);
Thread.Sleep(TimeSpan.FromSeconds(seconds));throw new Exception("Boom!");return 42 *seconds;
}static void Main(string[] args)
{try{
Task task = Task.Run(() => TaskMethod("Task 2", 2));int result =task.GetAwaiter().GetResult();
Console.WriteLine("Result: {0}", result);
}catch(Exception ex)
{
Console.WriteLine("Task 2 Exception caught: {0}", ex.Message);
}
Console.WriteLine("----------------------------------------------");
Console.WriteLine();
}
}
}
View Code
多个任务:
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static int TaskMethod(string name, intseconds)
{
Console.WriteLine("Task {0} is running on a thread id {1}. Is thread pool thread: {2}",
name, Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread);
Thread.Sleep(TimeSpan.FromSeconds(seconds));throw new Exception(string.Format("Task {0} Boom!", name));return 42 *seconds;
}public static void Main(string[] args)
{try{var t1 = new Task(() => TaskMethod("Task 3", 3));var t2 = new Task(() => TaskMethod("Task 4", 2));var complexTask =Task.WhenAll(t1, t2);var exceptionHandler = complexTask.ContinueWith(t =>Console.WriteLine("Result: {0}", t.Result),
TaskContinuationOptions.OnlyOnFaulted
);
t1.Start();
t2.Start();
Task.WaitAll(t1, t2);
}catch(AggregateException ex)
{
ex.Handle(exception=>{
Console.WriteLine(exception.Message);return true;
});
}
}
}
}
View Code
async/await的方式:
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static asyncTask ThrowNotImplementedExceptionAsync()
{throw newNotImplementedException();
}static asyncTask ThrowInvalidOperationExceptionAsync()
{throw newInvalidOperationException();
}static asyncTask Normal()
{awaitFun();
}staticTask Fun()
{return Task.Run(() =>{for (int i = 1; i <= 10; i++)
{
Console.WriteLine("i={0}", i);
Thread.Sleep(200);
}
});
}static asyncTask ObserveOneExceptionAsync()
{var task1 =ThrowNotImplementedExceptionAsync();var task2 =ThrowInvalidOperationExceptionAsync();var task3 =Normal();try{//异步的方式
Task allTasks =Task.WhenAll(task1, task2, task3);awaitallTasks;//同步的方式//Task.WaitAll(task1, task2, task3);
}catch(NotImplementedException ex)
{
Console.WriteLine("task1 任务报错!");
}catch(InvalidOperationException ex)
{
Console.WriteLine("task2 任务报错!");
}catch(Exception ex)
{
Console.WriteLine("任务报错!");
}
}public static voidMain()
{
Task task=ObserveOneExceptionAsync();
Console.WriteLine("主线程继续运行........");
task.Wait();
}
}
}
View Code
2.5、Task.FromResult的应用
usingSystem;usingSystem.Collections.Generic;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static IDictionary cache = new Dictionary()
{
{"0001","A"},
{"0002","B"},
{"0003","C"},
{"0004","D"},
{"0005","E"},
{"0006","F"},
};public static voidMain()
{
Task task = GetValueFromCache("0006");
Console.WriteLine("主程序继续执行。。。。");string result =task.Result;
Console.WriteLine("result={0}", result);
}private static Task GetValueFromCache(stringkey)
{
Console.WriteLine("GetValueFromCache开始执行。。。。");string result = string.Empty;//Task.Delay(5000);
Thread.Sleep(5000);
Console.WriteLine("GetValueFromCache继续执行。。。。");if (cache.TryGetValue(key, outresult))
{returnTask.FromResult(result);
}return Task.FromResult("");
}
}
}
View Code
2.6、使用IProgress实现异步编程的进程通知
IProgress只提供了一个方法void Report(T value)，通过Report方法把一个T类型的值报告给IProgress,然后IProgress的实现类Progress的构造函数接收类型为Action的形参，通过这个委托让进度显示在UI界面中。
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{static void DoProcessing(IProgressprogress)
{for (int i = 0; i <= 100; ++i)
{
Thread.Sleep(100);if (progress != null)
{
progress.Report(i);
}
}
}static asyncTask Display()
{//当前线程
var progress = new Progress(percent =>{
Console.Clear();
Console.Write("{0}%", percent);
});//线程池线程
await Task.Run(() =>DoProcessing(progress));
Console.WriteLine("");
Console.WriteLine("结束");
}public static voidMain()
{
Task task=Display();
task.Wait();
}
}
}
View Code
2.7、Factory.FromAsync的应用 (简APM模式(委托)转换为任务)(BeginXXX和EndXXX)
带回调方式的
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{private delegate string AsynchronousTask(stringthreadName);private static string Test(stringthreadName)
{
Console.WriteLine("Starting...");
Console.WriteLine("Is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
Thread.Sleep(TimeSpan.FromSeconds(2));
Thread.CurrentThread.Name=threadName;return string.Format("Thread name: {0}", Thread.CurrentThread.Name);
}private static voidCallback(IAsyncResult ar)
{
Console.WriteLine("Starting a callback...");
Console.WriteLine("State passed to a callbak: {0}", ar.AsyncState);
Console.WriteLine("Is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
Console.WriteLine("Thread pool worker thread id: {0}", Thread.CurrentThread.ManagedThreadId);
}//执行的流程是 先执行Test--->Callback--->task.ContinueWith
static void Main(string[] args)
{
AsynchronousTask d=Test;
Console.WriteLine("Option 1");
Task task = Task.Factory.FromAsync(
d.BeginInvoke("AsyncTaskThread", Callback, "a delegate asynchronous call"), d.EndInvoke);
task.ContinueWith(t=> Console.WriteLine("Callback is finished, now running a continuation! Result: {0}",
t.Result));while (!task.IsCompleted)
{
Console.WriteLine(task.Status);
Thread.Sleep(TimeSpan.FromSeconds(0.5));
}
Console.WriteLine(task.Status);
}
}
}
View Code
不带回调方式的
usingSystem;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceConsoleApp1
{classProgram
{private delegate string AsynchronousTask(stringthreadName);private static string Test(stringthreadName)
{
Console.WriteLine("Starting...");
Console.WriteLine("Is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
Thread.Sleep(TimeSpan.FromSeconds(2));
Thread.CurrentThread.Name=threadName;return string.Format("Thread name: {0}", Thread.CurrentThread.Name);
}//执行的流程是 先执行Test--->task.ContinueWith
static void Main(string[] args)
{
AsynchronousTask d=Test;
Task task = Task.Factory.FromAsync(
d.BeginInvoke, d.EndInvoke,"AsyncTaskThread", "a delegate asynchronous call");
task.ContinueWith(t=> Console.WriteLine("Task is completed, now running a continuation! Result: {0}",
t.Result));while (!task.IsCompleted)
{
Console.WriteLine(task.Status);
Thread.Sleep(TimeSpan.FromSeconds(0.5));
}
Console.WriteLine(task.Status);
}
}
}
View Code
//Task启动带参数和返回值的函数任务//下面的例子test2 是个带参数和返回值的函数。
private int test2(objecti)
{this.Invoke(new Action(() =>{
pictureBox1.Visible= true;
}));
System.Threading.Thread.Sleep(3000);
MessageBox.Show("hello:" +i);this.Invoke(new Action(() =>{
pictureBox1.Visible= false;
}));return 0;
}//测试调用
private voidcall()
{//Func funcOne = delegate(string s){ return "fff"; };
object i = 55;var t = Task.Factory.StartNew(new Func(test2), i);
}//= 下载网站源文件例子 == == == == == == == == == == == ==//HttpClient 引用System.Net.Http
private async Task< int> test2(objecti)
{this.Invoke(new Action(() =>{
pictureBox1.Visible= true;
}));
HttpClient client= newHttpClient();var a = await client.GetAsync("http://www.baidu.com");
Task s =a.Content.ReadAsStringAsync();
MessageBox.Show (s.Result);//System.Threading.Thread.Sleep(3000);//MessageBox.Show("hello:"+ i);
this.Invoke(new Action(() =>{
pictureBox1.Visible= false;
}));return 0;
}async private voidcall()
{//Func funcOne = delegate(string s){ return "fff"; };
object i = 55;var t = Task>.Factory.StartNew(new Func>(test2), i);
}//----------或者----------
private async voidtest2()
{this.Invoke(new Action(() =>{
pictureBox1.Visible= true;
}));
HttpClient client= newHttpClient();var a = await client.GetAsync("http://www.baidu.com");
Task s =a.Content.ReadAsStringAsync();
MessageBox.Show (s.Result);this.Invoke(new Action(() =>{
pictureBox1.Visible= false;
}));
}private voidcall()
{var t = Task.Run(newAction(test2));//相当于//Thread th= new Thread(new ThreadStart(test2));//th.Start();
}
Task启动带参数和返回值的函数任务