DotNet NB
string res = "";var concurrentDictionary = new ConcurrentDictionary<int, string>();var dictionary = new Dictionary<int, string>();dictionary.TryAdd(1, "aa");concurrentDictionary.TryAdd(1,"");var sw = new Stopwatch();sw.Start();Parallel.For(0, 1000000, i =>//Parallel使用并行循环{lock (dictionary){dictionary[i] = new Random().Next(1000, 9999).ToString();}});sw.Stop();Console.WriteLine("加锁写入dictionary {0}", sw.Elapsed);//wrinting to dictionary with a lock: 00:00:00.0633939sw.Restart();Parallel.For(0, 1000000, i =>{concurrentDictionary[i] = new Random().Next(1000, 9999).ToString();});sw.Stop();Console.WriteLine("concurrentdictionary写入时长 : {0}", sw.Elapsed);sw.Restart();Parallel.For(0, 1000000, i =>{lock (dictionary){res = dictionary[i];}});sw.Stop();Console.WriteLine("读取dictionary耗时: {0}", sw.Elapsed);sw.Restart();Parallel.For(0, 1000000, i =>{res = concurrentDictionary[i];});sw.Stop();Console.WriteLine("读取concurrentdictionary耗时: {0}", sw.Elapsed);Console.ReadLine();
结果如下
ConcurrentDictionary和Dictionary运行结果显示，读取写入的效率都是ConcurrentDictionary胜出，完美，也未出现线程安全的问题。注意环境关系可能略有差距。据说在多核多线程的情况下concurrentDictionary将有更好的性能表现。
面试官也可能问Dictionary怎么解决线程安全问题，如果答出使用ConcurrentDictionary一定是加分项。
注意，有网友指出ConcurrentDictionary使用依然会有线程安全问题，楼主目前没有发现，大家可以自己试一试。
dictionary.TryAdd(1, "aa");concurrentDictionary.TryAdd(1,"");
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