關於-c#字串三種逆轉方法及效能比較的另外看法c#字串三種逆轉方法及效能比較

原文：c#字串三種逆轉方法及效能比較

看到後覺得很奇怪，個人認為在很多情況下類庫方法肯定要比自己寫的方法效能好

原文作者傳入的字串，如果是傳入字元數組的話測試結果則大大出乎作者的意外。
修改代碼如下：

 class StringReverse    {        /// <summary>        /// 字串逆轉-StringBuilder實現        /// </summary>        /// <param name="str"></param>        /// <returns></returns>        public static string ReverseUsingStringBuilder(char[] str)        {            int length = str.Length;            StringBuilder sb = new StringBuilder(length);            for (int i = length - 1; i >= 0; i--)            {                sb.Append(str[i]);            }            return sb.ToString();        }        /// <summary>        /// 字串逆轉-CharArray實現        /// </summary>        /// <param name="str"></param>        /// <returns></returns>        public static string ReverseUsingCharArray(char[] str)        {            char[] arr = str;            Array.Reverse(arr);            return new string(arr);           // return string.Join(string.Empty,str.Reverse());                  }        /// <summary>        /// 字串逆轉-異或實現        /// </summary>        /// <param name="str"></param>        /// <returns></returns>        public static string ReverseUsingXor(char[] str)        {            char[] arr = str;            int l = arr.Length-1;            //交換值            for (int i = 0; i < l; i++, l--)            {                str[i] ^= str[l];                str[l] ^= str[i];                str[i] ^= str[l];            }            return new string(str);        }        public delegate string funcDelegate(char[] s);        /// <summary>        /// 測試方法        /// </summary>        /// <param name="description">方法描述</param>        /// <param name="func">測試方法</param>        /// <param name="times">執行次數</param>        /// <param name="str">測試字串</param>        public static void Benchmark(string description, funcDelegate func, int times, char[] str)        {            Stopwatch sw = new Stopwatch();            sw.Start();            for (int j = 0; j < times; j++)            {                func(str);            }            sw.Stop();            Console.WriteLine("方法{0}：調用{1}次,用時{2}.", description, times, sw.ElapsedTicks);        }        /// <summary>        /// 產生指定長度隨機字串        /// </summary>        /// <param name="length">字條串長度</param>        /// <returns></returns>        public static char[] RandomString(int length)        {            Random random = new Random();           // StringBuilder sb = new StringBuilder();            char[] sb=new char[length];            for (int i = 0; i < length; i++)            {                sb[i]=Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));            }            return sb;        }        static void Main(string[] args)        {            int[] lengths = new int[] { 1, 10, 15, 25, 50, 75, 100, 1000, 100000 };          //  int[] lengths = new int[] { 1, 10, 15, 25, 50, 75, 100};            foreach (int len in lengths)            {                //每個方法都執行10000次，力求精確                int iterations = 10000;                //產生隨機測試字串                char[] testString = StringReverse.RandomString(len);                          //列印測試資訊                StringReverse.Benchmark(String.Format("String Builder (測試字串長度為{0})", len), StringReverse.ReverseUsingStringBuilder, iterations, testString);                StringReverse.Benchmark(String.Format("Array.Reverse (測試字串長度為{0})", len), StringReverse.ReverseUsingCharArray, iterations, testString);                StringReverse.Benchmark(String.Format("Xor (測試字串長度為{0})", len), StringReverse.ReverseUsingXor, iterations, testString);                Console.WriteLine();            }            Console.Read();        }    }

　　測試結果：