C#中字典集合HashTable、Dictionary、ConcurrentDictionary三者区别

using System;
using System.Collections;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;

namespace WebApp
{
    class Program
    {
        static Hashtable _hashtable;
        static Dictionary<string, string> _dictionary;
        static ConcurrentDictionary<string, string> _conDictionary;
        static void Main(string[] args)
        {
            Compare(5000000);
            Console.ReadLine();
            Console.Read();
        }

        public static void Compare(int dataCount)
        {
            _hashtable = new Hashtable();
            _dictionary = new Dictionary<string, string>();
            _conDictionary = new ConcurrentDictionary<string, string>();
            Stopwatch stopWatch = new Stopwatch();

            // Hashtable
            stopWatch.Start();
            for (int i = 0; i < dataCount; i++)
            {
                _hashtable.Add("key" + i.ToString(), "Value" + i.ToString());
            }
            stopWatch.Stop();
            Console.WriteLine("HashTable插" + dataCount + "条耗时(毫秒)：" + stopWatch.ElapsedMilliseconds);

            //Dictionary
            stopWatch.Reset();
            stopWatch.Start();
            for (int i = 0; i < dataCount; i++)
            {
                _dictionary.Add("key" + i.ToString(), "Value" + i.ToString());
            }
            stopWatch.Stop();
            Console.WriteLine("Dictionary插" + dataCount + "条耗时(毫秒)：" + stopWatch.ElapsedMilliseconds);

            //ConcurrentDictionary
            stopWatch.Reset();
            stopWatch.Start();
            for (int i = 0; i < dataCount; i++)
            {
                _conDictionary.TryAdd("key" + i.ToString(), "Value" + i.ToString());
            }
            stopWatch.Stop();
            Console.WriteLine("ConcurrentDictionary插" + dataCount + "条耗时(毫秒)：" + stopWatch.ElapsedMilliseconds);

            // Hashtable
            stopWatch.Reset();
            stopWatch.Start();
            for (int i = 0; i < _hashtable.Count; i++)
            {
                var key = _hashtable[i];
            }
            stopWatch.Stop();
            Console.WriteLine("HashTable遍历时间(毫秒)：" + stopWatch.ElapsedMilliseconds);

            //Dictionary
            stopWatch.Reset();
            stopWatch.Start();
            for (int i = 0; i < _hashtable.Count; i++)
            {
                var key = _dictionary["key" + i.ToString()];
            }
            stopWatch.Stop();
            Console.WriteLine("Dictionary遍历时间(毫秒)：" + stopWatch.ElapsedMilliseconds);

            //ConcurrentDictionary
            stopWatch.Reset();
            stopWatch.Start();
            for (int i = 0; i < _hashtable.Count; i++)
            {
                var key = _conDictionary["key" + i.ToString()];
            }
            stopWatch.Stop();
            Console.WriteLine("ConcurrentDictionary遍历时间(毫秒)：" + stopWatch.ElapsedMilliseconds);
        }
    }
}