c# Thread类

现在C#已经建议摈弃使用 Suspend, Resume 暂停/恢复线程, 也尽量少用 Abort方法中断一个线程.

建议使用线程的同步手段有:  Mutex、ManualResetEvent、AutoResetEvent, Monitor.

下面再对此进行详细描述.

Thread类的构造函数有2类:

 一种是不带参数(ThreadStart 委托) --

public Thread(ThreadStart start);

另一种是带参数(ParameterizedThreadStart 委托) --

public Thread(ParameterizedThreadStart start);

ParameterizedThreadStart 委托签名:

public delegate void ParameterizedThreadStart(Object obj);

示例:

1. 不带参数:

// 定义线程方法:
private static void ThreadMain()
{
       Console.WriteLine("This is other thread main method.");
}
// 调用:
Thread mythread = new Thread(ThreadMain);
mythread.Start();

2. 带参数:

// 定义线程方法:
private static void MainThreadWithParameters(object o)
{
      Data d = (Data)o;  //类型转换
      Console.WriteLine("Running in a thread, received {0}", d.Message);
}

public struct Data
{
      public string Message;
}

// 调用:
var data = new Data { Message = "Info" };
Thread t2 = new Thread(MainThreadWithParameters);
t2.Start(data);  // 传入参数

3. 通过定义类传递参数:

// 定义存放数据和线程方法的类:
public class MyThread
{
   private string message;
   public MyThread(string data)
   {
      this.message = data;
   }
   public void ThreadMethod()
   {
      Console.WriteLine("Running in a thread, data: {0}", this.message);  
   }
}
// 调用
var obj = new MyThread("info");
Thread myThread = new Thread(obj.ThreadMethod); //ThreadStart 委托
mythread.Start(); 

C#中,Thread类有一个IsBackground 的属性.MSDN上对它的解释是:获取或设置一个值，该值指示某个线程是否为后台线程。

.Net中的线程,可以分为后台线程和前台线程。后台线程与前台线程并没有本质的区别，它们之间唯一的区别就是:后台线程不会防止应用程序的进程被终止掉。就是当前台线程都结束了的时候,整个程序也就结束了,即使还有后台线程正在运行,此时,所有剩余的后台线程都会被停止且不会完成.但是,只要还有一个前台线程没有结束,那么它将阻止程序结束.应用程序进程的存亡由前台线程决定而于后台线程无关.这就是它们的区别.改变线程从前台到后台不会以任何方式改变它在CPU协调程序中的优先级和状态。因为前台后线程与程序进程的优先级无关.下面的代码示例对比了前台线程与后台线程的行为。创建一个前台线程和一个后台线程。前台线程使进程保持运行，直到它完成它的 while 循环。前台线程完成后，进程在后台线程完成它的 while 循环之前终止。

using System;
using System.Threading;

class Test
{
    static void Main()
    {
        BackgroundTest shortTest = new BackgroundTest(10);
        Thread foregroundThread = 
            new Thread(new ThreadStart(shortTest.RunLoop));
        foregroundThread.Name = "ForegroundThread";

        BackgroundTest longTest = new BackgroundTest(50);
        Thread backgroundThread = 
            new Thread(new ThreadStart(longTest.RunLoop));
        backgroundThread.Name = "BackgroundThread";
        backgroundThread.IsBackground = true;

        foregroundThread.Start();
        backgroundThread.Start();
    }
}

class BackgroundTest
{
    int maxIterations;

    public BackgroundTest(int maxIterations)
    {
        this.maxIterations = maxIterations;
    }

    public void RunLoop()
    {
        String threadName = Thread.CurrentThread.Name;
        
        for(int i = 0; i < maxIterations; i++)
        {
            Console.WriteLine("{0} count: {1}", 
                threadName, i.ToString());
            Thread.Sleep(250);
        }
        Console.WriteLine("{0} finished counting.", threadName);
    }
}