.NET MD5加密 16位/32位

/// <summary>
/// MD5加密
/// </summary>
/// <param name="str"></param>
/// <param name="code"></param>
/// <returns></returns>
public static string Md5Encrypt(string str, int code)
{
    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);
    }
    else//32位加密
    {
        return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower();
    }
}