/// <summary>
/// MD5加密
/// </summary>
/// <param name="str">欲加密的字符串</param>
/// <param name="code">位数（16或32）</param>
/// <returns>加密后的字符串</returns>
        public static string md5(string str, int code)
        {
if (code == ) //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(, );
            }
else   //32位加密 
            {
return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower();
            }
        }