1. 线程的基本概念
简单的讲进程就是程序分配在内存当中，等待处理器进行处理，请记住线程会消耗大量的操作系统资源。多个线程共享一个物理处理器将导致处理器忙于处理管理这些进程，而无法运行程序。
使用线程通常是一个操作系统的任务，试图在一个单核CPU上并行执行计算任务是没有任何意义的，可能比顺序执行花费的时间更长。
为了更好的利用现代处理器的能力，使用多线程处理程序发挥出最好的作用，这需要组织多个线程间的通讯和相互同步。
下面将学习一下 线程的生命周期，和创建线程、挂起线程、线程等待、以及终止线程。
创建一个线程操作
static void Main(string[] args)
{
//创建一个新的线程来实现输出数字
Thread t = new Thread(PrintNumber);
t.Start();
//这一行代码是在创建了一个新的线程并行执行的
PrintNumber();
Console.ReadLine();
} static void PrintNumber()
{
Console.WriteLine("Starting...");
for (int i = 0; i < 10; i++)
{
Console.WriteLine(i);
}
}
从上面代码可以看出一个程序始终有一个主线程在执行，而Thread是创建一个新的线程执行。两者之间是同步执行的。
暂停线程
static void Main(string[] args)
{
//创建一个带暂停的进程
Thread t = new Thread(PrintNumberWithdelay);
t.Start();
//这一行就是始终执行的主线程经过（一个程序都有一个始终执行的主线程）
PrintNumber();
} static void PrintNumber()
{
Console.WriteLine("Starting...");
for (int i = 0; i < 10; i++)
{
Console.WriteLine(i);
}
}
static void PrintNumberWithdelay()
{
Console.WriteLine("暂停...");
for (int i = 0; i < 10; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(2));
Console.WriteLine(i);
}
}
很明显，主线程已经执行完毕，而新的线程在输出暂停以后还在继续执行。每次执行都会休眠2秒钟。
线程等待
那么如何不让主线程继续往下执行，而是等待新线程执行完毕再往下执行呢。
static void Main(string[] args)
{
//创建一个带暂停的进程
Thread t = new Thread(PrintNumberWithdelay);
t.Start();
t.Join();//线程等待
Console.WriteLine("执行完毕了"); }
static void PrintNumberWithdelay()
{
Console.WriteLine("暂停...");
for (int i = 0; i < 10; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(1));
Console.WriteLine(i);
}
}
终止线程
static void Main(string[] args)
{
//创建一个带暂停的进程
Thread t = new Thread(PrintNumberWithdelay);
t.Start();
Thread.Sleep(TimeSpan.FromSeconds(3));
t.Abort();//终止线程
Console.WriteLine("线程终止了");
}
这段代码是给线程注入了ThreadAbortException方法，导致线程被终结，这样操作是非常危险的，因为该异常可能会导致整个应用程序都崩溃。
可以使用 ResetAbort 方法来拒绝被终止。
检测线程状态
static void Main(string[] args)
{
//创建一个带暂停的进程
Thread t = new Thread(PrintNumberWithdelay);
Thread t1 = new Thread(DoNothing);
t1.Start();
t.Start();
for (int i = 0; i < 30; i++)
{
Console.WriteLine(t.ThreadState.ToString());
}
Thread.Sleep(TimeSpan.FromSeconds(3));
t.Abort();//终止线程
Console.WriteLine("线程终止了");
Console.WriteLine(t.ThreadState.ToString());
Console.WriteLine(t1.ThreadState.ToString());
} static void PrintNumberWithdelay()
{
Console.WriteLine("开始啦...");
Console.WriteLine(Thread.CurrentThread.ThreadState.ToString());
for (int i = 0; i < 10; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(1));
Console.WriteLine(i);
}
}
static void DoNothing()
{
Thread.Sleep(TimeSpan.FromSeconds(2));
}
当主程序定义了两个不同的线程，一个将会被终止，而另一个则会成功运行。线程状态位于Thread 对象的ThreadState属性中。ThreadState属性是一个C#枚举对象。
刚开始线程状态为Unstarted ，然后启动线程，并估计在一周期为30的迭代的区间中，线程状会从Running变为WitSleepJoin。
线程优先级
class ThreadSample
{
private bool _isStopped = false;
public void Stop()
{
_isStopped = true;
}
public void CountNumbers()
{
long counter = 0;
while (!_isStopped)
{
counter++;
}
Console.WriteLine("{0} 和 {1,11}" + " count={2,13}",
Thread.CurrentThread.Name,
Thread.CurrentThread.Priority,
counter.ToString("NO"));
}
} class Program
{
static void RunThreads()
{
var sample = new ThreadSample();
var threadOne = new Thread(sample.CountNumbers);
threadOne.Name = "ThreadOne";
var threadTwo = new Thread(sample.CountNumbers);
threadTwo.Name = "ThreadTwo"; threadOne.Priority = ThreadPriority.Highest;//优先级较高
threadTwo.Priority = ThreadPriority.Lowest;//优先级较低 threadOne.Start();
threadTwo.Start(); Thread.Sleep(TimeSpan.FromSeconds(2));
sample.Stop(); }
static void Main(string[] args)
{
Console.WriteLine("线程状态：{0}",Thread.CurrentThread.Priority);
Console.WriteLine("开始");
RunThreads();
Thread.Sleep(TimeSpan.FromSeconds(3));
Console.WriteLine("模拟CPU单核计算");
//让操作系统运行在第一个CPU第一个核心上
Process.GetCurrentProcess().ProcessorAffinity = new IntPtr(1);
RunThreads();//运行时间很长
Console.WriteLine("线程终止了");
} }
此程序只用于演示，通常中无需使用这种方式。
前台线程和后台线程
class ThreadSample
{
private readonly int _iterations;
public ThreadSample(int iterations)
{
_iterations = iterations;
}
public void CountNumbers()
{
for (int i = 0; i < _iterations; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(0.5));
Console.WriteLine("{0} 和 {1}",
Thread.CurrentThread.Name, i);
} }
} class Program
{
static void Main(string[] args)
{
var samppleforegroud = new ThreadSample(10);
var sampplebackgroup = new ThreadSample(20); var threadOne = new Thread(samppleforegroud.CountNumbers); threadOne.Name = "前台"; var threadTwo = new Thread(sampplebackgroup.CountNumbers); threadTwo.Name = "后台";
threadTwo.IsBackground = true; threadOne.Start();
threadTwo.Start(); } }
显示创建的是前台线程， ThreadTwo是后台线程 ，通过配置第一个线程会比第二个线程先完成，前台线程如果执行完毕，那么也会把后台线程终止掉。
向线程传递参数
class ThreadSample
{ private readonly int _iterations;
public ThreadSample(int iterations)
{
_iterations = iterations;
}
public void CountNumbers()
{
for (int i = 0; i < _iterations; i++)
{
Thread.Sleep(TimeSpan.FromSeconds(0.5));
Console.WriteLine("{0} 和 {1}",
Thread.CurrentThread.Name, i);
} }
} class Program
{
static void Count(object i)
{
CountNumbers((int)i);
} static void CountNumbers(int number)
{
Console.WriteLine(number);
} static void PrintNumber(int number)
{
Console.WriteLine(number);
} static void Main(string[] args)
{
var samppleforegroud = new ThreadSample(10); var threadOne = new Thread(samppleforegroud.CountNumbers);
threadOne.Name = "One";
threadOne.Start();
threadOne.Join();
Console.WriteLine("------------"); var threadTwo = new Thread(Count);
threadTwo.Name = "Two";
threadTwo.Start(8);
threadTwo.Join(); var threaThree = new Thread(() => CountNumbers(12));
threaThree.Name = "Three";
threaThree.Start();
threaThree.Join(); int i = 10;
var threaFour = new Thread(() => PrintNumber(i));
i = 20;
var threaFour1 = new Thread(() => PrintNumber(i));
threaFour.Start();
threaFour1.Start(); } }
使用Lock
abstract class CountBase
{
public abstract void Increment();
public abstract void Decrement(); } class Counter : CountBase
{
public int Count { get; private set; } public override void Increment()
{
Count++;
} public override void Decrement()
{
Count--;
}
} class CounterWithLock : CountBase
{
private readonly object _syncroot = new object(); public int Count { get; private set; }
public override void Increment()
{
lock (_syncroot)
{
Count++;
}
} public override void Decrement()
{
lock (_syncroot)
{
Count--;
}
}
} class Program
{
static void TestCouner(CountBase c)
{
for (int i = 0; i < 100000; i++)
{
c.Increment();
c.Decrement();
}
} static void Main(string[] args)
{
var c = new Counter(); var t1 = new Thread(() => TestCouner(c));
var t2 = new Thread(() => TestCouner(c));
var t3 = new Thread(() => TestCouner(c)); t1.Start();
t2.Start();
t3.Start();
t1.Join();
t2.Join();
t3.Join(); Console.WriteLine(c.Count); var c1 = new CounterWithLock(); t1 = new Thread(() => TestCouner(c));
t2 = new Thread(() => TestCouner(c));
t3 = new Thread(() => TestCouner(c)); t1.Start();
t2.Start();
t3.Start();
t1.Join();
t2.Join();
t3.Join(); Console.WriteLine(c.Count); } }
使用Monitor 锁定资源
为了避免死锁，则使用Monitor 类 来避免死锁。
Monitor.TryEnter(lock1,TimeSpan.FromSeconds(5));