测试目标：
用两组 50000 个字符串做包含(Contains)判断，分析性能差异。
50000个字符串集合测试结果：
Dictionary/ConcurrentDictionary 能在1-2毫秒完成50000个字符串集合的包含判断；
List 需要3秒，ConcurrentBag需要 23秒！
| 集合类型 | 耗时(毫秒) | 耗时倍数 |
| List.Contains | 3117 | 2940 |
| ConcurrentBag.Contains | 22796 | 21505 |
| Dictionary.ContainsKey | 1.06 | 1 |
| ConcurrentDictionary.ContainsKey | 1.97 | 2 |
使用建议
- 不建议使用ConcurrentBag，不如ConcurrentDictionary<T,bool> 效率高好用；
- 频繁调用的Contains不建议使用List，会成为性能瓶颈，建议使用Dictionary或ConcurrentDictionary；
- 在多线程代码中，建议使用ConcurrentDictionary，而不是lock+Dictionary。
附测试代码一：List.Contains
public static double TestListContains()
{List<string> a = new();List<string> b = new();for(int i = 0; i < 50000; i++){a.Add(i.ToString());b.Add((50000 - i - 1).ToString());}DateTime n = DateTime.Now;foreach(var item in a){if (b.Contains(item)){}}return (DateTime.Now - n).TotalMilliseconds;
}附测试代码二：ConcurrentBagContains
public static double TestConcurrentBagContains()
{List<string> a = new();ConcurrentBag<string> b = new();for (int i = 0; i < 50000; i++){a.Add(i.ToString());b.Add((50000 - i - 1).ToString());}DateTime n = DateTime.Now;foreach (var item in a){if (b.Contains(item)){}}return (DateTime.Now - n).TotalMilliseconds;
}附测试代码三：DictionaryContainsKey
public static double TestDictionaryContainsKey()
{List<string> a = new();Dictionary<string,bool> b = new();for (int i = 0; i < 50000; i++){a.Add(i.ToString());b.Add((50000 - i - 1).ToString(),true);}DateTime n = DateTime.Now;foreach (var item in a){if (b.ContainsKey(item)){}}return (DateTime.Now - n).TotalMilliseconds;
}附测试代码四：ConcurrentDictionaryContainsKey
public static double TestContains3()
{List<string> a = new();ConcurrentDictionary<string, bool> b = new();for (int i = 0; i < 50000; i++){a.Add(i.ToString());b.TryAdd((50000 - i - 1).ToString(), true);}DateTime n = DateTime.Now;foreach (var item in a){if (b.ContainsKey(item)){}}return (DateTime.Now - n).TotalMilliseconds;
}
