C#对某一字符md5加密

/// <summary>
/// 对某一字符md5加密 转载请注明来自 http://www.shang11.com /// </summary>
/// <param name="str"></param>
/// <param name="code">16与32位加密</param>
/// <returns></returns>
public  string MD5_Encrypt(string str, int code)
{
if (code == 16) //16位MD5加密（取32位加密的9~25字符）
{
return FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower().Substring(8, 16);
}
if (code == 32)
{
return FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower();
}
return str;
}