ConcurrentDictionary遍历的线程安全问题

Question

本帖最后由 yanx8844 于 2010-05-19 11:32:12 编辑

Answer 1

up谁来接分。自己测试了一下，遍历没有问题。
我的测试代码：
 ConcurrentDictionary<int, int> cities = new ConcurrentDictionary<int, int>();            Parallel.Invoke(
                () =>
                {
                    int i = 0;
                    while (true)
                    {
                        int j = i + 10;
                        for (; i < j; i++)
                        {
                            if (cities.TryAdd(i, i))
                                Console.WriteLine("++Add {0}", i);
                            Thread.Sleep(10);
                        }
                        i -= 5;
                        j = i + 5;
                        for (; i < j; i++)
                        {
                            int t;
                            if (cities.TryRemove(i, out t))
                                Console.WriteLine("--Remove {0}", i);
                            Thread.Sleep(10);
                        }
                    }
                },
                () =>
                {
                    while (true)
                    {
                        Console.WriteLine("***********************************************************");
                        foreach (var item in cities)
                        {
                            Console.WriteLine("<<Output {0}", item.Value);
                            Thread.Sleep(5);
                        }
                        Thread.Sleep(1000);
                    }
                });

Answer 2

关于ConcurrentDictionary 的迭代如果以下面的形式进行迭代，迭代的时候不会阻塞线程，但是会读到脏数据           foreach (var item in MyDictionary)
            {
                //其他代码
            }如果下面这种形式，迭代的结果将是MyDictionary某一时刻的快照，不包含脏数据           foreach (var item in MyDictionary.ToArray())
            {
                //其他代码
            }同时，ConcurrentDictionary 的Count, Keys, Values 属性也是某一时刻的快照