C#|C# 多线程初级汇总 C#多线程初级汇总

异步委托

创建线程的一种简单方式是定义一个委托，并异步调用它委托是方法的类型安全的引用Delegate类还支持异步地调用方法。在后台，Delegate类会创建一个执行任务的线程

投票，并检查委托是否完成了任务
- 所创建的Delegate类提供了BeginInvoke()方法，该方法中，可以传递用委托类型定义的输入参数。
- BeginInvoke()方法总是有AsyncCallback和Object类型的两个额外参数
- BeginInvoke()方法返回类型：IAsyncResult
- 代码示例

static void Main(string[] args) { // synchronous method call // TakesAWhile(1,3000); // asynchronous by using a delegate TakesAWhileDelegate dl = TakesAWhile; IAsyncResult ar = dl.BeginInvoke(1, 500, null, null); while (!ar.IsCompleted) { // doing something else in the main thread Console.Write("."); Thread.Sleep(50); } int result = dl.EndInvoke(ar); Console.WriteLine("result:{0}", result); }public delegate int TakesAWhileDelegate(int data, int ms); static int TakesAWhile(int data, int ms) { Console.WriteLine("TakesAWhile started"); Thread.Sleep(ms); Console.WriteLine("TakesAWhile completed"); return ++data; }

使用与IAsyncResult相关联的等待句柄
- 使用AsyncWaitHandle属性可以访问等待句柄
- 代码示例，在此将上述示例中的While循环更改一下即可，如下

while (true) { Console.Write("."); if (ar.AsyncWaitHandle.WaitOne(50, false)) { Console.WriteLine("Can get the result now"); break; } }

异步回调
- 在BeginInvoke()方法的第3个参数中，可以传递一个满足AsyncCallback委托的需求的方法
- 代码示例

TakesAWhileDelegate dl = TakesAWhile; dl.BeginInvoke(1, 500, TakesAWhileCompleted, dl); for (int i = 0; i < 100; i++) { Console.Write("."); Thread.Sleep(50); }

static void TakesAWhileCompleted(IAsyncResult ar) { if (ar == null) throw new ArgumentNullException("ar"); TakesAWhileDelegate dl = ar.AsyncState as TakesAWhileDelegate; Trace.Assert(dl != null, "Invalid object type"); int result = dl.EndInvoke(ar); Console.WriteLine("result:{0}", result); }

Thread类

Thread类可以创建和控制线程
默认情况，Thread类创建线程是前台线程。线程池中的线程总是后台线程。
只要有一个前台线程在运行，应用程序的进程就在运行。Thread类创建线程时，可以设置IsBackground属性，以确定该线程时前台线程还是后台线程
【C#|C# 多线程初级汇总】代码示例

var t1 = new Thread(ThreadMain) { Name = "MyNewThread", IsBackground = false }; t1.Start(); Console.WriteLine("Main thread ending now.");

static void ThreadMain() { Console.WriteLine("Thread {0} started", Thread.CurrentThread.Name); Thread.Sleep(3000); Console.WriteLine("Thread {0} completed", Thread.CurrentThread.Name); }

线程池

ThreadPool类托管，在需要时增减池中线程的线程数，直到最大的线程数
ThreadPool.QueueUserWorkItem()方法，传递一个WaitCallback类型的委托
代码示例

int nWorkerThreads; int nCompletionPortThreads; ThreadPool.GetMaxThreads(out nWorkerThreads, out nCompletionPortThreads); Console.WriteLine("Max worker threads:{0},I/O completion threads:{1}", nWorkerThreads, nCompletionPortThreads); for (int i = 0; i < 5; i++) { ThreadPool.QueueUserWorkItem(JobForAThread); }

static void JobForAThread(object state) { for (int i = 0; i < 3; i++) { Console.WriteLine("loop{0},running inside pooled thread{1}", i, Thread.CurrentThread.ManagedThreadId); Thread.Sleep(50); } }

任务

.NET 4包含新名称空间 System.Threading.Tasks，它包含的类抽象出了线程功能。在后台使用ThreadPool.
启动新任务
- 实例化TaskFactory类，在其中把TaskMethod()方法传递给StartNew()方法
- 使用Task类的构造函数，调用Task类的Start()方法
- 示例代码

//using task factory TaskFactory tf = new TaskFactory(); Task t1 = tf.StartNew(TaskMethod); //using the task factory via a task Task t2 = Task.Factory.StartNew(TaskMethod); //using Task constructor Task t3 = new Task(TaskMethod); t3.Start(); Task t4 = new Task(TaskMethod, TaskCreationOptions.PreferFairness); t4.Start();