using System;
using System.Threading;

class Example
{
    // Create a new Mutex. The creating thread does not own the mutex. 
    private static Mutex mut = new Mutex();
    private const int numIterations = 1;
    private const int numThreads = 3;

    static void Main()
    {
        // Create the threads that will use the protected resource. 
        for(int i = 0; i < numThreads; i++)
        {
            Thread newThread = new Thread(new ThreadStart(ThreadProc));
            newThread.Name = String.Format("Thread{0}", i + 1);
            newThread.Start();
        }

        // The main thread exits, but the application continues to 
        // run until all foreground threads have exited.
    }

    private static void ThreadProc()
    {
        for(int i = 0; i < numIterations; i++)
        {
            UseResource();
        }
    }

    // This method represents a resource that must be synchronized 
    // so that only one thread at a time can enter. 
    private static void UseResource()
    {
        // Wait until it is safe to enter, and do not enter if the request times out.
        Console.WriteLine("{0} is requesting the mutex", Thread.CurrentThread.Name);
        if (mut.WaitOne(1000)) {
           Console.WriteLine("{0} has entered the protected area", 
               Thread.CurrentThread.Name);

           // Place code to access non-reentrant resources here. 

           // Simulate some work.
           Thread.Sleep(5000);

           Console.WriteLine("{0} is leaving the protected area", 
               Thread.CurrentThread.Name);

           // Release the Mutex.
              mut.ReleaseMutex();
           Console.WriteLine("{0} has released the mutex", 
                             Thread.CurrentThread.Name);
        }
        else {
           Console.WriteLine("{0} will not acquire the mutex", 
                             Thread.CurrentThread.Name);
        }
    }
}
// The example displays output like the following: 
//       Thread1 is requesting the mutex 
//       Thread1 has entered the protected area 
//       Thread2 is requesting the mutex 
//       Thread3 is requesting the mutex 
//       Thread2 will not acquire the mutex 
//       Thread3 will not acquire the mutex 
//       Thread1 is leaving the protected area 
//       Thread1 has released the mutex

 mutex.WaitOne();
 mutex.WaitOne();
 mutex.WaitOne();
 mutex.WaitOne();
。。
。。

mutex.ReleaseMutex();//如果已经占有 那么OK
mutex.ReleaseMutex();//调用第二次直接异常

Mutex mutex = new Mutex(true,"mutex1");

Mutex mutex = Mutex.OpenExisting("mutex1")