using System;
using System.IO;

namespace Test_CS
{
    class Program
    {
        const string fileName = @"E:\file.bin";

        static void Main(string[] args)
        {
            try
            {
                using (FileStream fileStream = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
                using (BinaryReader binReader = new BinaryReader(fileStream))
                using (BinaryWriter binWriter = new BinaryWriter(fileStream))
                {
                    // Пишем в поток
                    binWriter.Write(true);
                    binWriter.Write("Строка");
                    binWriter.Write(2.5);
                    binWriter.Write((byte)255);
                    // Указатель на начало
                    fileStream.Seek(0, SeekOrigin.Begin);
                    // Читаем и выводим
                    Console.WriteLine("Bool:{0}\nString:{1}\nDouble:{2}\nByte:{3}",
                        binReader.ReadBoolean(), binReader.ReadString(), binReader.ReadDouble(), binReader.ReadByte());
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            finally
            {
                Console.ReadKey();
            }
        }
    }
}

Bool:True
String:Строка
Double:2,5
Byte:255