public static void ToFile(MobilePhone obj)
    {

        FileStream fs = new FileStream("C://Users//Bohdan//Desktop//Новая папка (2)//data.xml", FileMode.OpenOrCreate);
        XmlSerializer xser = new XmlSerializer(typeof(MobilePhone));
        xser.Serialize(fs, obj);
        Console.WriteLine("Serialization to File done");
    }