【C#】Dictionary的TryGetValue和Contains效率对比：TryGetValue效率并不一定更好

许多文章都推荐大家在C#的Dictionary中使用TryGetValue而不是先ContainsKey判断然后再取值，通过源码我们很容易理解：

这是TryGetValue的源码：

        public bool TryGetValue(TKey key, out TValue value)
        {
            if (key == null)
            {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
            }
            lock(_lock)
            {
                VerifyIntegrity();
                return TryGetValueWorker(key, out value);
            }
        }

        private bool TryGetValueWorker(TKey key, out TValue value)
        {
            int entryIndex = FindEntry(key);
            if (entryIndex != -1)
            {
                Object primary = null;
                Object secondary = null;
                _entries[entryIndex].depHnd.GetPrimaryAndSecondary(out primary, out secondary);
                // Now that we've secured a strong reference to the secondary, must check the primary again
                // to ensure it didn't expire