Но не знаю как сделать поддержку циклов в графе объекта.
Для .NET 2.0.
Используется Dynamic Method.
Прирост в скорости при десериализации приблизительно в 5 раз, при сериализации в 2 раза.
Вот результаты теста:

Для 10000 объектов
BinaryFormatter serialize - 00:00:02.5504643, stream length = 25620000
BinaryFormatter desirialize - 00:00:02.7247557
CustomFormatter serialize - 00:00:00.9539868, stream length = 11730000
CustomFormatter desirialize - 00:00:00.5176641, 5,2635593485598
или для 50000 объектов
BinaryFormatter serialize - 00:00:13.6380023, stream length = 130750000
BinaryFormatter desirialize - 00:00:14.5414160
CustomFormatter serialize - 00:00:05.7686300, stream length = 63050000
CustomFormatter desirialize - 00:00:02.7774915, 5,23544923254071

Код теста

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

namespace Chardex
{

    class Program
    {
        static void Main(string[] args)
        {
            for (int k = 0; k < 10; k++)
            {
                CustomFormatter f = new CustomFormatter();
                MemoryStream ms = new MemoryStream();
                BinaryFormatter f2 = new BinaryFormatter();
                MemoryStream ms2 = new MemoryStream();

                SuperClass sc = new SuperClass();

                int count = 10000;

                Stopwatch sw = new Stopwatch();
                sw.Start();
                for (int i = 0; i < count; i++)
                {
                    f2.Serialize(ms2, sc);
                }
                sw.Stop();

                Console.WriteLine("BinaryFormatter serialize - " + sw.Elapsed + ", stream length = " + ms2.Length);

                ms2.Position = 0;

                sw.Reset();
                sw.Start();
                for (int i = 0; i < count; i++)
                {
                    SuperClass sc2 = (SuperClass)f2.Deserialize(ms2);
                }
                sw.Stop();

                Console.WriteLine("BinaryFormatter desirialize - " + sw.Elapsed);
                double ticks = sw.ElapsedTicks;

                sw.Reset();
                sw.Start();
                for (int i = 0; i < count; i++)
                {
                    f.Serialize(ms, sc);
                }
                sw.Stop();

                Console.WriteLine("CustomFormatter serialize - " + sw.Elapsed + ", stream length = " + ms.Length);

                ms.Position = 0;

                sw.Reset();
                sw.Start();
                for (int i = 0; i < count; i++)
                {
                    SuperClass sc2 = (SuperClass)f.Deserialize(ms);
                }
                sw.Stop();

                Console.WriteLine("CustomFormatter desirialize - " + sw.Elapsed + ", " + ticks / (double)sw.ElapsedTicks);

                Console.WriteLine();
            }
        }
    }

    [Serializable]
    public class SuperClass
    {
        int intFld = 0;
        Test testObj = new Test();
        Dictionary<DateTime, Test> testDic = new Dictionary<DateTime, Test>();
        int[] testArr = new int[] { 0, 1, 2, 3, 4 };
        List<Guid> testList = new List<Guid>();

        public SuperClass()
        {
            testObj.t = new Test2();
            intFld = 100;
            testDic[DateTime.Now] = new Test();
            testDic[DateTime.Now] = new Test();
            testDic[DateTime.Now] = new Test();
            testDic[DateTime.Now] = new Test();
            testDic[DateTime.Now] = new Test();
            testList.Add(Guid.NewGuid());
            testList.Add(Guid.NewGuid());
            testList.Add(Guid.NewGuid());
        }
    }
    [Serializable]
    public class Test
    {
        private int val = 500;
        private int test = 25;
        private int test2 = 25;
        private int tes42 = 25;
        private string testStre = "lalalal";
        public Test2 t;
    }
    [Serializable]
    public class Test2
    {
        private int val = 500;
        private int test = 25;
        private int test2 = 25;
        private int tes42 = 25;
        private string testStre = "lalalal";
    }

}

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