1 class CompareChange 2     { 3         private static int i = 0; 4         public static System.Threading.AutoResetEvent changeSignal = new System.Threading.AutoResetEvent(false);//同步信号 5  6         public static void test() 7         { 8             ThreadSafe ts = new ThreadSafe(); 9 10             System.Threading.ThreadPool.QueueUserWorkItem((obj) =>11             {12                 Console.WriteLine("modifying-thread is waiting for signal");13                 CompareChange.changeSignal.WaitOne();14                 Console.WriteLine("modifying-thread received the signal");15                 CompareChange.i++;16                 ts.Total = CompareChange.i;17                 Console.WriteLine("modifying-thread modify the CompareChange.i");18                 CompareChange.changeSignal.Set();19                 Console.WriteLine("modifying-thread send the complete signal");20             });21 22             System.Threading.ThreadPool.QueueUserWorkItem((obj) =>23             {24                 ts.AddToTotal(20);25             });26             27             Console.ReadLine();28         }29     }30 31     public class ThreadSafe32     {33         // totalValue contains a running total that can be updated 34         // by multiple threads. It must be protected from unsynchronized  35         // access. 36         private int totalValue = http://www.mamicode.com/0;37         private int times = 0;38         // The Total property returns the running total. 39         public int Total40         {41             get { return totalValue; }42             set { totalValue =http://www.mamicode.com/ value; }43         }44 45         // AddToTotal safely adds a value to the running total. 46         public int AddToTotal(int addend)47         {48             int initialValue, computedValue;49             do50             {51                 this.times++;52                 if (this.times == 2)53                     Console.WriteLine("orignal value has changed.it‘s the "+this.times.ToString()+"th times to run the process");54                 // Save the current running total in a local variable.55                 initialValue =http://www.mamicode.com/ totalValue;56 57                 Console.WriteLine("sending the modifying signal");58                 CompareChange.changeSignal.Set();59 60                 // Add the new value to the running total.61                 computedValue = http://www.mamicode.com/initialValue + addend;62 63                 Console.WriteLine("waiting for modifying-completely signal");64                 CompareChange.changeSignal.WaitOne();65 66                 // CompareExchange compares totalValue to initialValue. If 67                 // they are not equal, then another thread has updated the 68                 // running total since this loop started. CompareExchange 69                 // does not update totalValue. CompareExchange returns the 70                 // contents of totalValue, which do not equal initialValue, 71                 // so the loop executes again.72             } while (initialValue != System.Threading.Interlocked.CompareExchange(73                 ref totalValue, computedValue, initialValue));74             // If no other thread updated the running total, then  75             // totalValue and initialValue are equal when CompareExchange 76             // compares them, and computedValue is stored in totalValue. 77             // CompareExchange returns the value that was in totalValue 78             // before the update, which is equal to initialValue, so the  79             // loop ends. 80             Console.WriteLine("process is over");81             // The function returns computedValue, not totalValue, because 82             // totalValue could be changed by another thread between 83             // the time the loop ends and the function returns. 84             return computedValue;85         }86     }

运行结果：

modifying-thread is waiting for signal
sending the modifying signal
waiting for modifying-completely signal
modifying-thread received the signal
modifying-thread modify the CompareChange.i
modifying-thread send the complete signal
orignal value has changed.it‘s the 2th times to run the process
sending the modifying signal
waiting for modifying-completely signal
process is over