c#集合类的线程安全

叁歲伎倆 2022-06-09 14:19 325阅读 0赞

**原文网址:http://www.cnblogs.com/Clingingboy/archive/2010/12/06/1897534.html**

即位于System.Collections命名空间下的集合,如Hashtable,ArrayList,Stack,Queue等.其均提供了线程同步的一个实现

# 集合线程同步的问题 #

public class Demo8
    {
        ArrayList list = new ArrayList(1000000);
        public Demo8()
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(Task1));
            ThreadPool.QueueUserWorkItem(new WaitCallback(Task2));
        }
    
        public void Task1(object obj)
        {
            for (int i = 0; i < 500000; i++)
            {
                list.Add(i);
            }
    
            Console.WriteLine(DateTime.Now);
            Console.WriteLine("Task1 count {0}", list.Count);
        }
    
        public void Task2(object obj)
        {
            for (int i = 0; i < 500000; i++)
            {
                list.Add(i);
            }
    
            Console.WriteLine("Task2 count {0}", list.Count);
        }
    }

[![image][]][image 1]

与预期结果不同

# 调整为线程同步的集合 #

每种数据类型都包含一个静态的Synchronized方法,如

ArrayList list = ArrayList.Synchronized(new ArrayList(1000000));

调整后的结果

[![image][image 2]][image_image 2]   
以下为注意点：

1.  IsSynchronized判断集合是否为线程同步
2.  其内部通过给SyncRoot属性加锁进行同步(即Monitor.Enter)

# 自己控制锁 #

public class Demo8
    {
        ArrayList list = new ArrayList(1000000);
        public Demo8()
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(Task1));
            ThreadPool.QueueUserWorkItem(new WaitCallback(Task2));
        }
    
        public void Task1(object obj)
        {
            lock (list.SyncRoot)
            {
                for (int i = 0; i < 500000; i++)
                {
                    list.Add(i);
                }
            } 
           
            Console.WriteLine(DateTime.Now);
            Console.WriteLine("Task1 count {0}", list.Count);
        }
    
        public void Task2(object obj)
        {
            lock (list.SyncRoot)
            {
                for (int i = 0; i < 500000; i++)
                {
                    list.Add(i);
                }
            }
            Console.WriteLine("Task2 count {0}", list.Count);
        }
    }

[![image][image 3]][image_image 3]

这样的结果显然好看点.内部实现是在Add方法中做锁定.效果自然不是很好.

其他集合类也是类似的操作

[image]: /images/20220609/430ca3ad4b614e77ac2bca794cf04007.png
[image 1]: http://images.cnblogs.com/cnblogs_com/Clingingboy/Windows-Live-Writer/c_97F4/image_2.png
[image 2]: http://images.cnblogs.com/cnblogs_com/Clingingboy/Windows-Live-Writer/c_97F4/image_thumb_1.png
[image_image 2]: /images/20220609/34bb1f3eb75c4106ae55e3b430daba26.png
[image 3]: http://images.cnblogs.com/cnblogs_com/Clingingboy/Windows-Live-Writer/c_97F4/image_thumb_2.png
[image_image 3]: /images/20220609/e5a3de4e9d614635970f2245054c9a21.png