public string md5(string str,int code) //code 16 或 32
{
      if (str != "")
      {
          if (code == 16) //16位MD5加密（取32位加密的9~25字符）
          {
              return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower().Substring(8, 16);
          }

          if (code == 32) //32位加密
          {
              return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower();
          }
      }
     
   return "00000000000000000000000000000000";
}