Network Programming

1
Network Programming

• Chapter 2
• Streams in .NET

2
Basic Outline

• Streams in .NET
• Stream Manipulation
• Serialisation

3
Introduction

• A stream is an abstract representation of a
  sequence of bytes (e.g. file, I/O device or
  TCP/IP socket)
• Abstraction allows us to access different devices
  in the same manner (like with inheritance)

4
Streams in .NET

• Stream class
• Abstract class
• Perform binary I/O operations
• TextReader TextWriter classes
• BinaryReader BinaryWriter classes

5
Streams in .NET

• Synchronous and Asynchronous I/O
• Stream class provides for both synchronous
  asynchronous
• Stream Class
• FileStream Class
• Reading and Writing with the FileStream Class
• BufferedStream Class
• MemoryStream Class
• NetworkStream Class
• CryptoStream Class

6
Synchronous I/O

• Default setting
• Simplest method
• Blocks processing until operation is complete
  (disadvantage)
• Not suitable for operations over a network
• Not good choice for large files over low
  bandwidth
• Can simulate asynchronous I/O by threading

7
Asynchronous I/O

• Allows other processing
• Operating system notifies caller when I/O
  processing is done
• Needs separate notification mechanism
• Useful when application needs to process other
  tasks while doing I/O
• A separate thread is created for each I/O thread
  (higher O/S overhead)

8
Streams in .NET

• Synchronous and Asynchronous I/O
• Stream Class
• FileStream Class
• Reading and Writing with the FileStream Class
• BufferedStream Class
• MemoryStream Class
• NetworkStream Class
• CryptoStream Class

9
Stream Class
System.Security.Cryptography
System.Security.Cryptography.CryptoStream
10
Stream Class

• Base class System.IO
• Stream is base class for all other stream classes

11
Classes Derived From the Stream Class
12
Stream Members
13
Synchronous Methods for Reading from and Writing
to a Stream
14
Asynchronous Methods for Reading from and Writing
to a Stream
15
Methods for Managing a Stream
16
Streams in .NET

• Synchronous and Asynchronous I/O
• Stream Class
• FileStream Class
• Reading and Writing with the FileStream Class
• BufferedStream Class
• MemoryStream Class
• NetworkStream Class
• CryptoStream Class

17
FileStream Class

• One of the most widely used of the Stream-derived
  classes
• Handles files and standard input and output
  devices
• Several ways to create a FileStream object

18
Creating a FileStream Instance with a File Path

• Specify a path to a file
• Default buffer is 8192 bytes
• Buffer size may be changed in constructor
• Methods of creating a FileStream
• Specifying the File Path and Mode
• Specifying File Access
• Specifying Sharing Permissions
• Specifying Buffer Size
• Specifying Synchronous or Asynchronous State

19
FileMode Options
20
FileMode Syntax

• To create a FileStream object that creates a new
  file called c\Networking\MyStream.txt, you would
  use the following
• //Using file path and file mode
• FileStream inF new FileStream(C\\Networking\\M
  yStream.txt, FileMode.CreateNew)

21
FileAccess Options
22
FileAccess Syntax

• You can use the CanRead and CanWrite properties
  to check the FileAccess permission given to the
  file
• To create a new file called c\Networking\MyStream
  .txt with write-only access
• //Using file path, file mode and file access
• FileStream inF new FileStream(C\\Networking\\M
  yStream.txt, FileMode.CreateNew,
  FileAccess.Write)

23
FileShare Options
24
FileShare Syntax

• Create a FileStream instance using the FileMode,
  FileAccess and FileShare properties
• //Using file path, file mode, file access and
  sharing permission
• //Open file for writing, other processes will get
  read-only access
• FileStream inF new FileStream
  (C\\Networking\\MyStream.txt, FileMode.Open,
  FileAccess.Write, FileShare.Read)

25
Specifying Buffer Size

• You can also create a FileStream instance by
  specifying the size of the buffer in addition to
  the parameters discussed previously. Here we set
  the size of the buffer to 1000 bytes
• //using path, mode, access, sharing permission
  and buffer size
• FileStream inF new FileStream(C\\Networking\\M
  yStream.txt, FileMode.Open, FileAccess.Write,
  FileShare.Read, 1000)
• If the buffer size specified is between 0 and 8
  bytes, the actually buffer is set to 8 bytes

26
Specifying Synchronous or Asynchronous State

• //Using path, mode, access, sharing permission,
  buffer size and specifying asynchronous
  operations
• FileStream outF new FileStream(C\\Networking\\
  MyStream.txt, FileMode.Open, FileAccess.Write,
  FileShare.Read, 1000, true)

27
File Handle

• A file handle is a unique identifier that the
  operating system assigns to a file when the file
  is opened or created
• A file handle is represented using the IntPrt
  structure, which represents an integer of
  platform-specific length.
• Using the file handle, you may specify several
  properties of the stream
• //Create FileStream Instance
• FileStream inF new FileStream(
  C\Neworking\\MyStream.txt, FileMode.Open)
• Get the file Handle
• InterPtr fHanld infHandle

28
Streams in .NET

• Synchronous and Asynchronous I/O
• Stream class provides for both synchronous
  asynchronous
• Stream Class
• FileStream Class
• Reading and Writing with the FileStream Class
• BufferedStream Class
• MemoryStream Class
• NetworkStream Class
• CryptoStream Class

29
Reading Writing

• Synchronous I/O
• Stream class
• Asynchronous I/O

30
Synchronous I/O

• Stream class
• Read method
• Write method
• Example
• Performs synchronous I/O operations
• Seek method sets the position within the stream
• Need System.IO namespace
• Need System.Text (convert strings to byte arrays)

31
Synchronous I/O

• using System
• using System.Collections.Generic
• using System.Text
• using System.IO
• namespace SyncIO
• class Program

Note additional namespace(s)
32
Synchronous I/O

• static void Main(string args)
• //Create FileStream instance
• FileStream synF new FileStream("SyncDemo.txt",
  FileMode.OpenOrCreate)
• //this will open our file if it exists
  otherwise a new file is created.

33
Synchronous I/O

• //A character is converted to a byte and then
  written in a file using the WriteByte method
• //After the byte is written, the file position
  is automatically incremented by 1.
• Console.WriteLine("--Writebyte Method demo--")
• synF.WriteByte(Convert.ToByte('A'))

34
Synchronous I/O

• //Converting a string to a byte array (with the
  GetBytes method of the Encoding class in
  System.Text
• //Write takes three parameters
• // the byte array to write
• // the position or offset in the array from
  where to start writing
• // the length of data to be written
• Console.WriteLine("--Write method demo--")
• byte writeBytes Encoding.ASCII.GetBytes(" is
  the first character.")
• synF.Write(writeBytes, 0, writeBytes.Length)

35
Synchronous I/O

• //Reading the data from the file
• //When reading or writing on a FileStream, the
  current position(or pointer)of the file
  automatically
• //increases by the number of bytes read or
  written.
• //set pointer at origin (start of file or start
  of stream)
• synF.Seek(0, SeekOrigin.Begin)
• //Now we can read. We'll read a single byte
  with the ReadByte method first.
• //A byte is read from the stream (with the
  position automatically increased by 1) and
  converted by to char.
• Console.WriteLine("--Readbyte Method demo--")
• //Read byte and display
• Console.WriteLine("First character is -gt "
  Convert.ToChar(synF.ReadByte()))

36
Synchronous I/O

• //Now we read the remainder of the file with
  the Read method.
• //This method takes 3 parameters
• // A byte array that will store the data read
• // the position or offset in the array from
  where to start reading
• // the number of bytes to read
• //Because we want to read all of the remaining
  bytes in the file, we want to read in synF.Length
  - 1 bytes
• //Use of Read method
• Console.WriteLine("--Read Method demo--")
• //Allocate buffer
• byte readBuf new bytesynF.Length - 1
• //Read file
• synF.Read(readBuf, 0, Convert.ToInt32(synF.Length
  - 1))

37
Synchronous I/O

• //The byte array is then converted to string
  using the GetString method of the Encoding Class
• //Display contents
• Console.WriteLine("The rest of the file is "
  Encoding.ASCII.GetString(readBuf))
• //close the file
• synF.Close()
• Console.WriteLine("Press a key to continue.")
• Console.ReadLine()

38
Asynchronous I/O

• FileStream opens asynchronously when you pass
  true to the useAsync flag
• A special call-back mechanism is needed to
  implement asynchronous I/O, and an AsyncCallback
  delegate provides a way for client applications
  to implement this call-back mechanism.
• This call-back delegate is supplied to the
  BeginRead or BeginWrite method

39
Asynchronous I/O

• using System
• using System.Collections.Generic
• using System.Text
• using System.IO
• using System.Threading
• namespace AsyncDemo
• class Program
• //Stream object for reading
• static FileStream fileStrm
• //Buffer to read
• static byte readBuff

40
Asynchronous I/O

• //We declare an AsyncCallback delegate field for
  the callback function
• //AsyncCallback delegate
• static AsyncCallback Callback
• //In the Main method, we initialize our callback
  delegate to point to the Callback function method
• //This is the method that will be called when
  the end of the aynchronous read operation is
  signalled

41
Asynchronous I/O

• static void Main(string args)
• Callback new AsyncCallback(CallBackFunction)
• //now we can initialise our FileStream object,
  specifying asynchronous operations
• fileStrm new FileStream("Test.txt",
  FileMode.Open, FileAccess.Read, FileShare.Read,
  64, true)
• readBuff new bytefileStrm.Length
• //we can use the BeginRead method to initiate
  asynchronous read opeations on the stream.
• //The callback delegate is passed to the
  BeginRead method as its second-to-last parameter.
• //Call async read
• fileStrm.BeginRead(readBuff, 0,
  readBuff.Length, Callback, null)

42
Asynchronous I/O

• //Data will be read from FileStream while we
  continue with other activities.
• //Here we simply give the appearance of doing
  some other work by looping and every so often
  putting the main thread to sleep
• //Once the loop has finished, the FileStream
  object is closed.
• //Simulation of main execution
• for (long i 0 i lt 5000 i)
• if (i 1000 0)
• Console.WriteLine("Executing in Main - "
  i.ToString())
• Thread.Sleep(10)
• //end of if
• //end of for long
• fileStrm.Close()
• Console.WriteLine("Press a key to continue.")
• Console.ReadLine()
• //end of Main

43
Asynchronous I/O

• static void CallBackFunction(IAsyncResult
  asyncResult)
• //Gets called when read operation has completed
• int readB fileStrm.EndRead(asyncResult)
• if (readB gt 0)
• Console.WriteLine(Encoding.ASCII.GetString(readBu
  ff, 0, readB))
• //end of if
• //end of CallBackFunction

44
Streams in .NET

• Synchronous and Asynchronous I/O
• Stream class provides for both synchronous
  asynchronous
• Stream Class
• FileStream Class
• Reading and Writing with the FileStream Class
• BufferedStream Class
• MemoryStream Class
• NetworkStream Class
• CryptoStream Class

45
Buffered Stream Class

• A buffer is a reserved area of memory used for
  storing temporary data.
• Its main purpose is to improve I/O performance,
  and its often used to synchronise data transfer
  between devices of different speeds. Many online
  media applications use buffers as intermediate
  storage.
• BufferedStream Class
• Stream object
• Generally used with .NetworkStream to store data
  in memory
• FileStream Class has its own internal buffer
• MemoryStream Class does not require buffering

46
Buffered Stream Class

• using System
• using System.Collections.Generic
• using System.Text
• using System.IO
• using System.Threading
• namespace BufferedStreamDemo
• class Program
• static void Main(string args)
• FileStream fStr new
  FileStream("BufferDemo.txt", FileMode.OpenOrCreate
  )
• byte writeBytes
  Encoding.ASCII.GetBytes("The difference between
  genius and stupidity is that genius has its
  limits.")
• fStr.Write(writeBytes, 0,
  writeBytes.Length)
• Console.WriteLine("Message written")
• fStr.Seek(0, SeekOrigin.Begin)
• readBufStream(fStr)
• Console.WriteLine("Press a key to
  continue")

47
Buffered Stream Class

• //Takes a stream object parameters, wraps it in a
  buffered stream object and performs a read
  operaton
• //Reading Buffered Stream
• public static void readBufStream(Stream st)
• //Compose BufferedStream
• BufferedStream bf new BufferedStream(st)
• byte inData new Bytest.Length
• //Read and display buffered data
• bf.Read(inData, 0, Convert.ToInt32(st.Length))
• Console.WriteLine(Encoding.ASCII.GetString(inData
  ))

48
Memory Stream Class

• Situation where application needs data frequently
  (e.g. lookup table)
• Storing data in file
• Cause delays
• Reduce performance of application
• Use MemoryStream Class for cases where data needs
  to be stored in memory
• MemoryStream Class is used for fast, temporary
  storage

49
Memory Stream Class

• using System
• using System.Collections.Generic
• using System.Text
• using System.IO
• using System.Threading
• namespace MemoryStreamDemo
• class Program
• static void Main(string args)
• //Create empty Memory stream
• MemoryStream ms new MemoryStream()
• byte memData Encoding.ASCII.GetByt
  es("This will go in Memory!")
• //Write data
• ms.Write(memData, 0, memData.Length)

50
Memory Stream Class

• //Set pointer at origin
• ms.Position 0
• byte inData new byte100
• //Read memory
• ms.Read(inData, 0, 100)
• Console.WriteLine(Encoding.ASCII.GetSt
  ring(inData))
• Stream str new FileStream("MemOutput
  .txt", FileMode.OpenOrCreate, FileAccess.Write)
• ms.WriteTo(str)
• str.Close()

51
Network Stream Class

• NetworkStream class is in the System.Net.Sockets
  namespace
• Unbuffered stream
• Does not support random access to data
• BufferedStream class is often used to buffer the
  NetworkStream

52
Properties of Network Stream
53
Network Stream Class

• Each NetworkStream constructor requires at least
  one Socket.
• A NetworkStream object can be retrieved from a
  TcpClient

54
Network Stream Example (Listener)

• using System
• using System.Collections.Generic
• using System.Text
• using System.Net
• using System.IO
• using System.Net.Sockets
• namespace TCPListenerDemo
• class Program
• static void Main(string args)
• try
• //Create TCP Lister to listen on
  port 5001
• IPAddress ipAddress
  Dns.GetHostEntry("localhost").AddressList0
• TcpListener listener new
  TcpListener(ipAddress, 5001)

55
Network Stream Example (Listener)

• //Start listening
• listener.Start()
• //AcceptClient accepts a
  connection request, returning a TcpClient
• TcpClient tc listener.AcceptTcpC
  lient()
• //we use the TcpClient's
  GetStream to create a NetworkStream object
• NetworkStream stm
  tc.GetStream()
• //now we can read data as we have
  with the other streams, using the Read method
• byte readBuf new byte100
• stm.Read(readBuf, 0, 100)
• //Display data
• Console.WriteLine(Encoding.ASCII.G
  etString(readBuf))
• stm.Close()
• //end of try
• catch (Exception ex)
• Console.WriteLine(ex.ToString())
• //end of catch

56
Network Stream Client

• using System
• using System.Collections.Generic
• using System.Text
• using System.Net
• using System.IO
• using System.Net.Sockets
• namespace TCPClient
• class Program
• static void Main(string args)
• try
• //Create TCP Client
• TcpClient client new
  TcpClient()

57
Network Stream Client

• //Connect using hostname and port
• client.Connect("localhost",
  5001)
• //Get network stream instance for
  sending data
• NetworkStream ns
  client.GetStream()
• //Now that we have our
  NetworkStream, sending data follows the same
  process as we've used with the other streams
• byte sendBytes
  Encoding.ASCII.GetBytes("This data has come from
  another place!")
• ns.Write(sendBytes, 0,
  sendBytes.Length)
• //Finally, close our client
• client.Close()
• //end of try
• catch (Exception ex)
• Console.WriteLine(ex.Message)
• Console.WriteLine("The listener
  has probably not started.")
• //end of catch

58
CryptoStream Class

• Secure data
• Encrypt/decrypt with secret key
• CryptoStream derives from Stream class
• CryptoStream constructor takes 3 parameters
• Stream to be used
• Cryptographic transformation
• Specific read/write access to the cryptographic
  stream
• Any cryptographic service provider that
  implements the ICryptoTransform interface can be
  used

59
CryptoStream Class

• using System
• using System.Collections.Generic
• using System.Text
• using System.IO
• using System.Security.Cryptography
• namespace cryptDemo
• class Program
• static void Main(string args)
• SymmetricAlgorithm des null
• int answer Menu(ref des)
• //A file stream is created to save
  encrypted data
• FileStream fs new
  FileStream("SecretFile.dat", FileMode.Create,
  FileAccess.Write)
• //The interface helps define the
  basic operation of our cryptographic
  transformation
• ICryptoTransform desencrypt
  des.CreateEncryptor()
• //Wrap cryptoStream around fileStream

60
CryptoStream Class

• //Write byte array to cryptoStream
• cryptoStream.Write(byteArrayInput, 0,
  byteArrayInput.Length)
• cryptoStream.Close()
• fs.Close()
• //Time to
  Decrypt//
• //Create file stream to read
  encrypted file back
• FileStream fsRead new
  FileStream("SecretFile.dat", FileMode.Open,
  FileAccess.ReadWrite)
• byte encByte new
  bytefsRead.Length
• fsRead.Read(encByte, 0,
  encByte.Length)
• Console.WriteLine("Encrypted Message
  0", Encoding.ASCII.GetString(encByte))
• //set the position of the within the
  filestream back to 0 before decrypting
• fsRead.Position 0
• //Create DES Decryptor from our des
  instance
• ICryptoTransform desdecrypt
  des.CreateDecryptor()
• CryptoStream cryptoStreamDecr new
  CryptoStream(fsRead, desdecrypt,
  CryptoStreamMode.Read)
• byte decrByte new
  bytefsRead.Length
• cryptoStreamDecr.Read(decrByte, 0,
  (int)fsRead.Length)
• string output Encoding.Unicode.GetSt
  ring(decrByte)

61
CryptoStream Class

• private static int Menu(ref SymmetricAlgorithm
  des)
• bool isCorrect true
• int answer 0
• //Ask the user to choose a service
  provider
• //All service providers derived from
  the SymmetricAlgorithm class have a single secret
  key that is used for both encrypting and
  decrypting
• do
• isCorrect true
• Console.WriteLine("Select Service
  Provider for CryptoStream")
• Console.WriteLine("1
  DESCryptoServiceProvider")
• Console.WriteLine("2
  RC2CryptoServiceProvider")
• Console.WriteLine("3
  RijndaelManaged")
• Console.WriteLine("4
  TripleDESCryptoServiceProvider")
• Console.WriteLine("5
  SymmetricAlgorithm")
• Console.Write("Enter your choice
  ")
• //create des object
• switch (Console.ReadLine())

62
CryptoStream Class

• answer 2
• break
• case "3" des new
  RijndaelManaged()
• answer 3
• break
• case "4" des new
  TripleDESCryptoServiceProvider()
• answer 4
• break
• case "5" des
  SymmetricAlgorithm.Create()
• answer 5
• break
• default
• Console.WriteLine("Wro
  ng Selection")
• isCorrect false
• break
• //end of default
• //end of switch
• while (!(isCorrect))

63
Basic Outline

• Streams in .NET
• Stream Manipulation
• Introduction
• Encoding String Data
• Binary Files
• Text Reader
• Text Writer
• Serialisation

64
Stream Manipulation

• System.IO namespace provides classes and methods
  for manipulating different data types in streams

65
Encoding String Data

• Without knowing what the bytes mean, transmitted
  data is meaningless
• Encoding Class in System.Text
• Handles UNICODE characters

66
Encoding Classes and Uses
67
Encoding Class Methods
68
Encoding Class Methods
69
Encoding String Data

• using System
• using System.Text
• using System.IO
• namespace EncodingStringData
• class Program
• static void Main(string args)
• string test "This is our test
  string."
• byte asciiBytes
• byte unicodeBytes
• byte UTF7Bytes
• //convert our test string into the
  three different encodings
• asciiBytes Encoding.ASCII.GetBytes(t
  est)
• Console.WriteLine("ASCII Byte
  String")

70
Encoding String Data

• unicodeBytes Encoding.Unicode.GetBytes(
  test)
• Console.WriteLine("Unicode Byte
  String")
• Console.WriteLine("Unicode Encoding
  0 bytes", unicodeBytes.Length)
• DisplayArray(unicodeBytes)
• Console.WriteLine("Effect of
  converting to Unicode")
• string unicodeString
  Encoding.ASCII.GetString(unicodeBytes)
• Console.WriteLine(unicodeString)
• Console.WriteLine()
• UTF7Bytes Encoding.UTF7.GetBytes(tes
  t)
• Console.WriteLine("UTF7 Byte
  String")
• Console.WriteLine("UTF7 Encoding 0
  bytes", UTF7Bytes.Length)
• DisplayArray(UTF7Bytes)
• Console.WriteLine("Effect of
  converting to UTF7")
• string utf7String
  Encoding.ASCII.GetString(UTF7Bytes)
• Console.WriteLine(utf7String)
• Console.WriteLine()

71
Encoding String Data

• static void DisplayArray(byte b)
• for (int i 0 i lt b.Length i)
• Console.Write(bi " ")
• Console.WriteLine()
• //end of DisplayArray

72
Basic Outline

• Streams in .NET
• Stream Manipulation
• Introduction
• Encoding String Data
• Binary Files
• BinaryReader
• BinaryWriter
• Text Reader
• Text Writer
• Serialisation

73
Binary Files

• System.IO namespace contains
• BinaryReader
• BinaryWriter
• Used for working with primitive data types from
  streams
• Each class is created around an existing Stream

74
BinaryReader

• Default is UTF-8 encoding
• Custom encoding is possible (at instantiation)
• BinaryReader
• Read
• Read bytes from the stream and advances the
  position in the stream, returning -1 if the end
  of the stream is reached
• PeekChar
• To read without advancing the position in the
  stream
• Returns -1 if the end of the stream is reached or
  if the stream does not support seeking

75
Binary Reader Methods
76
Binary Reader Methods
77
Binary Writer

• Used for writing primitive types in binary format
  to a stream
• Writing to the stream is achieved with the Write
  method.
• To move around the stream, the Seek method sets
  the position in the Stream as with the Seek
  method of the Stream.
• Standard management methods utilised
• Close
• Flush

78
Binary Reading and Writing Example

• using System
• using System.IO
• namespace BinaryReaderAndWriter
• class Program
• static void Main(string args)
• double angle, sinAngle
• //Create a file stream called fStream
  that creates a file called "Sines.dat"
• //Stream specifies write access
• FileStream fStream new
  FileStream("Sines.dat", FileMode.Create,
  FileAccess.Write)
• BinaryWriter bWriter new
  BinaryWriter(fStream)
• //We calculate the sine of angles
  between 0 and 90 degrees at 5 degree intervals
• //We have to convert the angle in
  degrees to radians before we can calculate the
  sine
• //Then we use Write to output these
  values to the stream
• for (int i 0 i lt 90 i 5)

79
Binary Reading and Writing Example

• //----------Reading from
  File--------------
• FileStream fStrm new
  FileStream("Sines.dat", FileMode.Open,
  FileAccess.Read)
• BinaryReader bReader new
  BinaryReader(fStrm)
• int endOfFile
• //use the ReadDouble method to read
  the data back in
• //If this method tries to read beyond
  hte end of the stream, an exception will be
  thrown,
• //so we use the PeekChar method to
  detect the end of the file without advancing the
  position
• do
• endOfFile bReader.PeekChar()
• if (endOfFile ! -1)
• angle bReader.ReadDouble()
• sinAngle bReader.ReadDouble(
  )
• Console.WriteLine("0
  1", angle, sinAngle)
• //end of if
• while (endOfFile ! -1)
• bReader.Close()

80
Basic Outline

• Streams in .NET
• Stream Manipulation
• Introduction
• Encoding String Data
• Binary Files
• Text Reader
• Working with StreamReader
• Text Writer
• Working with StreamWriter
• Serialisation

81
Text Reader

• Used for reading text or characters in a stream
• Its an abstract class from which StreamReader
  and StringReader derive
• The text is read in by a StringReader is stored
  as a StringBuilder, rather than a plain string

82
TextReader Class Methods
83
TextReader Class Methods
84
Working with StreamReader

• Used to read characters from a byte stream
• Default is UTF-8 encoding
• Provides forward-only access to the stream

85
Example

• public static string fileName _at_"TextOut.txt"
• static void Main(string args)
• Stream fs new FileStream(fileName,
  FileMode.Open, FileAccess.Read)
• //Using Stream Object
• StreamReader sReader new StreamReader(fs)
• string data
• int line 0
• while ((data sReader.ReadLine()) ! null)
• Console.WriteLine("Line 0 1 Position
  2", line, data, sReader.BaseStream.Position)
• //sReader.DiscardBufferedData()
• //Set position using seek property of underlying
  stream
• sReader.BaseStream.Seek(0, SeekOrigin.Begin)
• Console.WriteLine()

86
TextWriter

• Abstract class
• Outputs a sequential series of characters
• StreamWriter and StringWriter are derived from
  TextWriter

87
TextWriter Class Methods
88
TextWriter Class Methods
89
Working with StreamWriter

• Used for writing characters in a stream
• Default is UTF-8 Encoding
• StreamWriter constructor is overloaded
• Can pass a stream object to a StreamWriter (gives
  greater control over file accessibility)

90
StreamWriter

• static void Main(string args)
• string s1 "The length of a film should be
  directly related to the endurance of the human
  bladder. - Alfred Hitchcock."
• string s2 "USA Today has come out with a new
  survey Apparently three out of four people make
  up 75 percent of the population.-David
  Letterman."
• Stream fs new FileStream("TextOut.txt",
  FileMode.OpenOrCreate, FileAccess.Write)
• //Using Stream Object
• StreamWriter sWriter new StreamWriter(fs)
• //Display the encoding type
• Console.WriteLine("Encoding Type 0",
  sWriter.Encoding.ToString())
• //Display Format Provider
• Console.WriteLine("Format Provider 0",
  sWriter.FormatProvider.ToString())
• sWriter.WriteLine("Today is 0.",
  DateTime.Today.DayOfWeek)
• sWriter.WriteLine(s1)
• sWriter.WriteLine(s2)

91
StreamWriter

• for (int i 0 i lt 5 i)
• sWriter.WriteLine("Value 0, its square is
  1.", i, i i)
• //end of for
• //Writing array
• sWriter.Write("Arrays can be written ")
• char myArray new char 'a', 'r', 'r',
  'a', 'y'
• sWriter.Write(myArray)
• sWriter.WriteLine("\r\nAnd parts of arrays can
  be written.")
• sWriter.Write(myArray, 0, 3)
• sWriter.Close()
• fs.Close()
• Console.WriteLine("Press a key to continue.")
• Console.ReadLine()

92
Basic Outline

• Streams in .NET
• Stream Manipulation
• Introduction
• Encoding String Data
• Binary Files
• Text Reader
• Text Writer
• Serialisation
• Serialising into XML Format
• Serialising with Formatter Objects

93
Serialisation

• Serialisation is the process of taking objects
  and converting their state information into a
  form that can be stored or transported.
• The stored or transported object can then be
  de-serialised to re-create the original state of
  object.
• Key areas where serialisation is beneficial
• Object availability A component can be saved in
  a file made available whenever required
• Object lifetime Saving the object with its state
  increases its life. In normal practice, when you
  close an application, all associated objects are
  destroyed automatically
• Object use within networked applications The
  complex form of the object has been transformed
  to a format that is suitable for transferring
  across a network and possibly through firewalls
• Object reliability The saved object can be
  re-created as is.

94
Serialising into XML format

• XML has advantages
• Transform system-specific state information into
  text (which is easily transported over a network)
• XML disadvantage
• Does not preserve the type of the various fields
  involved (it serialises properties/fields into
  XML format)
• XMLSerializer class in System.XML.Serialization
  namespace
• Rules for serializing a class
• The class must support a default public
  constructor with no parameters
• Only public properties that support both get and
  set operations and public data members are
  persisted

95
Serialisation using XML

• The Customer class
• public class Customer
• public int CustomerID
• public string CustomerName
• public DateTime SignUpDate
• private decimal currentCredit
• public void SetCurrentCredit(decimal c)
• currentCredit c
• public decimal GetCurrentCredit()
• return currentCredit
• //end of Customer

Notice the public and private fields
96
Serialising Customer to XML

• using System
• using System.IO
• using System.Text
• using System.Xml.Serialization
• static void Main(string args)
• //prepare object for serialisation
• Customer cm new Customer()
• cm.CustomerID 12
• cm.CustomerName "Stuart Little"
• cm.SignUpDate DateTime.Now
• cm.SetCurrentCredit(76.23M)
• Console.WriteLine("Now Serialising...")
• //Create Stream Writer object
• StreamWriter writer new StreamWriter("Customer
  .xml")
• //Create Serialiser
• XmlSerializer serializer new
  XmlSerializer(typeof(Customer))
• //Serialise the object

97
Serialising an object

• Console.WriteLine("Now Deserialising...")
• //Open and create stream
• Stream streamOut new FileStream("Customer.xml",
  FileMode.Open, FileAccess.Read)
• XmlSerializer deserial new XmlSerializer(typeo
  f(Customer))
• //Deserialise the sotred stream
• Customer recm (Customer)deserial.Deserialize(
  streamOut)
• streamOut.Close()
• //Display sate of object
• Console.WriteLine("Customer ID 0",
  recm.CustomerID)
• Console.WriteLine("Customer name 0",
  recm.CustomerName)
• Console.WriteLine("Sign up Date 0",
  recm.SignUpDate)
• Console.WriteLine("Current Credit 0",
  recm.GetCurrentCredit())
• Console.ReadLine()

98
Serialising with Formatter Objects

• Within the System.Runtime.Serialization.Formatters
  namespace lie the tools for serializing object
  state into formats such as binary or SOAP
• The BinaryFormatter class provides functionality
  for serializing objects into binary format, and
  the SoapFormatter class serialises into the SOAP
  format
• Binary format serialises object state and also
  assembly information allowing exact reproduction
  of an object and its types. It also produces a
  compact format
• The SOAP format is more verbose (wordy), but it
  allows your object state to be passed to a web
  service

99
The Steps for serialising an object/class

• Mark the class with the Serializable attribute
  to make it serializable
• Prepare the objects state for serialization
• Create a new formatter object BinaryFormatter
  for binary format or SoapFormatter for SOAP
• Call the Serialize method of the formatter
  object, passed in the stream to which to output
  the results and the object to be serialized

100
Deserializing

• Specify the format for deserializing the object
  with the relevant formatter object
• Call the Deserialize method of this formatter
  object
• Cast the object returned to the type you wish to
  re-create

101
Serializing

• The Serializable attribute is not inherited,
  thus derived types are not automatically
  serialisable.
• To protect confidential data, you can make a
  field NonSerialized any such fields will not
  be serialised (says the book need further
  testing to verify)

102
Summary