class UserPrefs
    {
        enum Color { Black, White };
        private Color _textColor = Color.Black;
        private Color _bgColor = Color.White;
        private string _userName = "Sn00py";
        public string UserName
        {
            get { return _userName; }
        }
        // ...
    }

    [Serializable]
    class UserPrefs
    {
        enum Color { Black, White };
        private Color _textColor = Color.Black;
        private Color _bgColor = Color.White;
        private string _userName = "Sn00py";
        public string UserName
        {
            get { return _userName; }
        }
        // ...
    }

            BinaryFormatter bf = new BinaryFormatter();
            UserPrefs up = new UserPrefs();

            using (FileStream fs = new FileStream("user.dat",FileMode.Create, FileAccess.Write,FileShare.None))
            {
                bf.Serialize(fs, up);
            }

 using (Stream fStream = File.OpenRead("user.dat"))
            {
                Something st = (UserPrefs)bf.Deserialize(fStream);
            }

using System;
using System.Collections;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
namespace ConsoleApplication24
{
    [Serializable]
    class UserPrefs
    {
        enum Color { Black, White };
        private Color _textColor = Color.Black;
        private Color _bgColor = Color.White;
        private string _userName = "Sn00py";
        public string UserName
        {
            get { return _userName; }
        }
        // ...
    }
    class Class2
    {
        public static void Main()
        {
            BinaryFormatter bf = new BinaryFormatter();
            UserPrefs up = new UserPrefs();
            Console.WriteLine("--> Current UserPrefs Username is: {0}", up.UserName);
            Console.WriteLine();
            Console.WriteLine("--> Serializing UserPrefs Class...");
            using (FileStream fs = new FileStream("user.dat",FileMode.Create, FileAccess.Write,FileShare.None))
            {
                bf.Serialize(fs, up);
            }
            Console.ReadLine();
            Console.WriteLine("--> Deserializing UserPrefs Class...");
            using (Stream fStream = File.OpenRead("user.dat"))
            {
                UserPrefs upTest = (UserPrefs)bf.Deserialize(fStream);
                Console.WriteLine(upTest.UserName.ToString());
            }
        }
    }
}