将32位MD5摘要串转换为128位二进制字符串

将32为MD5摘要串转换为128位二进制字符串：

         /// <summary>
         /// 将字符串转成二进制
         /// </summary>
         /// <param name="s">源字符串</param>
         /// <returns>二进制串</returns>
         internal static string ConvertStringToBinary(string s)
         {
             if (s.IsNullOrWhiteSpace())
             {
                 throw new ArgumentNullException("源字符串为空", s);
             }
             if (s.Length != )
             {
                 throw new ArgumentNullException("源字符串长度无效", s);
             }
             var bitBuilder = new StringBuilder();
             for (var i = ; i < s.Length; i += )
             {
                 var tem = Convert.ToInt32(s.Substring(i, ), );
                 bitBuilder.Append(Convert.ToString(tem, ).PadLeft(, ''));
             }
             return bitBuilder.ToString();
         }