streams & file input/output basics c#.net development version 1.1

Streams & File Input/Output Basics

C# .Net Development

Version 1.1

Copyright © 2003-2011 by Dennis A. Fairclough all rights reserved. 2

byte stream of bytes byte

Stream

source(writer)

sink(reader)

4 3 2 1 0

What do stream methods do?Open() //opens a streamClose() //closes and flushes a streamFlush() //flushes buffered data in a streamWrite() //writes to a stream (writer is better)Read() //reads from a stream (reader is better)throw IOException


A word to the wise! Wrap ALL stream access messages and code in a try-catch-finally!

try{

//stream access messages }catch(IOException ioexp){

//exception response code}catch(Exception exp){

//exception response code}finally{

//stream clean-up, flush and close code}


Streams System.IO

Namespace Much like other languages

Text Seeking in file

Behavior is sometimes undefined Binary

Can seek in file File IO

File Input/Output Serializing data

C# has much easier ways of doing this, but will look into older techniques first


Classes Used for File I/O (Visual Studio Help File)

Directory provides static methods for creating, moving, and enumerating through directories and subdirectories.

Directory class provides static methods. DirectoryInfo class provides instance methods. DirectoryInfo provides instance methods for creating, moving, and enumerating through directories and subdirectories. DriveInfo provides instance methods for accessing information about a drive.

File provides static methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of a FileStream. File class provides static methods. FileInfo class provides instance methods. FileInfo provides instance methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of a FileStream. FileInfo contains instance methods.

FileStream supports random access to files through its Seek method. FileStream opens files synchronously by default, but supports asynchronous operation as well. FileSystemInfo is the abstract base class for FileInfo and DirectoryInfo.

Path provides methods and properties for processing directory strings in a cross-platform manner.

DeflateStream provides methods and properties for compressing and decompressing streams using the Deflate algorithm.

GZipStream provides methods and properties for compressing and decompressing streams. By default, this class uses the same algorithm as the DeflateStream class, but can be extended to use other compression formats. SerialPort provides methods and properties for controlling a serial port file resource.

File, FileInfo, DriveInfo, Path, Directory, and DirectoryInfo are sealed


Common I/O Stream Classes (Visual Studio Help)

BufferedStream is a Stream that adds buffering to another Stream such as a NetworkStream. (FileStream already has buffering internally, and a MemoryStream does not need buffering.) A BufferedStream can be composed around some types of streams in order to improve read and write performance. A buffer is a block of bytes in memory used to cache data, thereby reducing the number of calls to the operating system.

CryptoStream links data streams to cryptographic transformations. Although CryptoStream derives from Stream, it is not part of the System.IO namespace, but is in the System.Security.Cryptography namespace.

MemoryStream is a nonbuffered stream whose encapsulated data is directly accessible in memory. This stream has no backing store and might be useful as a temporary buffer.

NetworkStream represents a Stream over a network connection. Although NetworkStream derives from Stream, it is not part of the System.IO namespace, but is in the System.Net.Sockets namespace.


Classes Used for Reading from and Writing to Streams (Visual Studio Help File)

BinaryReader and BinaryWriter read and write encoded strings and primitive data types from and to Streams.

StreamReader reads characters from Streams, using Encoding to convert characters to and from bytes.

StreamReader has a constructor that attempts to ascertain what the correct Encoding for a given Stream is, based on the presence of an Encoding-specific preamble, such as a byte order mark.

StreamWriter writes characters to Streams, using Encoding to convert characters to bytes.

StringReader reads characters from Strings. StringReader allows you to treat Strings with the same API, so your output can be either a Stream in any encoding or a String.

StringWriter writes characters to Strings. StringWriter allows you to treat Strings with the same API, so your output can be either a Stream in any encoding or a String.

TextReader is the abstract base class for StreamReader and StringReader. While the implementations of the abstract Stream class are designed for byte input and output, the implementations of TextReader are designed for Unicode character output.

TextWriter is the abstract base class for StreamWriter and StringWriter. While the implementations of the abstract Stream class are designed for byte input and output, the implementations of TextWriter are designed for Unicode character input.


Text Files

Data converted to char’s and written as bytes. Data read as bytes and converted to char’s

and converted to appropriate data type. Two bytes per character (unicode) Remember Internationalization (Localization)!

Output element is a string containing the text to be written as bytes.

Returned element is bytes converted to a string containing the text read.


Text File Basicsusing System;using System.IO;using System.Windows.Forms; //Must add reference for MessageBox and SaveFileDialog

namespace TextFiles_101{ static class TextFileProgram { const int MAX = 5; [STAThread] static void Main() { FileStream _fs = null; StreamWriter _sw = null; StreamReader _sr = null; SaveFileDialog _SaveDlg = null; string _FileName = null; string _TempStg = null; try { _SaveDlg = new SaveFileDialog(); _SaveDlg.Filter = "Text File (*.txt)|*.txt|All Files (*.*)|*.*"; _SaveDlg.FilterIndex = 1; _SaveDlg.ShowDialog(); _FileName = _SaveDlg.FileName; _fs = new FileStream(_FileName, FileMode.Create, FileAccess.Write); _sw = new StreamWriter(_fs); for (int i = 1; i <=MAX; i++) _sw.WriteLine(i); _sw.Close(); _sw = null; _fs = new FileStream(_FileName, FileMode.Open, FileAccess.Read); _sr = new StreamReader(_fs); _TempStg = _sr.ReadToEnd(); _fs.Seek(0, SeekOrigin.Begin); for (int i = 0; i <=MAX; i++) { _TempStg = _sr.ReadLine(); if (_TempStg == null) break; Console.WriteLine(_TempStg); } _sr.Close(); _sr = null; } catch (IOException ioexp) { MessageBox.Show("IOException " + ioexp.Message, "IOException", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Error); } catch (Exception exp) { MessageBox.Show("Unknown Exception " + exp.Message, "Unknown Exception", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Error); } finally { if (_sw != null) _sw.Close(); if (_sr != null) _sr.Close(); if (_fs != null) _fs.Close(); } Console.ReadLine(); } }//end class TextFileProgram}//end namespace TextFiles_101

FileMode Enumeration CreateNew

Specifies that the operating system should create a new file. This requires FileIOPermissionAccess..::.Write. If the file already exists, an IOException is thrown.

Create Specifies that the operating system should create a new file. If the file already exists, it will be overwritten. This

requires FileIOPermissionAccess..::.Write. System.IO.FileMode.Create is equivalent to requesting that if the file does not exist, use CreateNew; otherwise, use Truncate.

Open Specifies that the operating system should open an existing file. The ability to open the file is dependent on the value

specified by FileAccess. A System.IO..::.FileNotFoundException is thrown if the file does not exist.

OpenOrCreate Specifies that the operating system should open a file if it exists; otherwise, a new file should be created. If the file is

opened with FileAccess.Read, FileIOPermissionAccess..::.Read is required. If the file access is FileAccess.Write then FileIOPermissionAccess..::.Write is required. If the file is opened with FileAccess.ReadWrite, both FileIOPermissionAccess..::.Read and FileIOPermissionAccess..::.Write are required. If the file access is FileAccess.Append, then FileIOPermissionAccess..::.Append is required.

Truncate Specifies that the operating system should open an existing file. Once opened, the file should be truncated so that its

size is zero bytes. This requires FileIOPermissionAccess..::.Write. Attempts to read from a file opened with Truncate cause an exception.

Append Specifies that a file is opened and the file if it exists and seeks to the end of the file, or creates a new file.

FileMode.Append can only be used in conjunction with FileAccess.Write. Attempting to seek to a position before the end of the file will throw an IOException and any attempt to read fails and throws an NotSupportedException.


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FileAccess Enumeration Read

Read access to the file. Data can be read from the file. Combine with Write for read/write access.

Write Write access to the file. Data can be written to the

file. Combine with Read for read/write access. ReadWrite

Read and write access to the file. Data can be written to and read from the file.



Binary File Basicsclass DataClass{ string ss,se; int i; char c; bool b; FileStream fs; BinaryWriter bw; BinaryReader br; public DataClass(FileStream filestream) { fs = filestream; c = 'a'; b = true; } public void WriteThySelf() { bw = new BinaryWriter(fs); bw.Write("Start"); bw.Write(i); bw.Write(c); bw.Write(b); bw.Write("End"); bw.Flush(); } public void SeekThySelf() { fs.Seek(6,SeekOrigin.Begin); } public void ReadThySelf() { DataClass ret = new DataClass(fs); br = new BinaryReader(fs); //ret.ss = br.ReadString(); ret.i = br.ReadInt32(); ret.c = br.ReadChar(); ret.b = br.ReadBoolean(); ret.se = br.ReadString(); } public void CleanUpThySelf() { if (bw != null) bw.Close(); if (br != null) br.Close(); if (fs != null) fs.Close(); }}//end class DataClass


Binary File Basics (Main())using System;using System.IO;using System.Windows.Forms;

static class Program{ static public void Main() { DataClass dc1 = null; try { dc1 = new DataClass(new FileStream(@"G:\Moo.bin", FileMode.Create, FileAccess.ReadWrite)); dc1.WriteThySelf(); dc1.SeekThySelf(); dc1.ReadThySelf(); } catch (IOException ioexp) { MessageBox.Show("IOException -> " + ioexp.Message); } catch (Exception exp) { MessageBox.Show("Exception -> " + exp.Message); } finally { MessageBox.Show("finally -> Cleaning Up"); dc1.CleanUpThySelf(); } }}//end class Program


Directory static class

Manage directory stuff duh!


Directory

Much like File But deals with directories!


Directory Members Delete() Exists() GetCreationTime() GetCurrentDirectory() GetDirectories() GetDirectoryRoot() GetFileSystemEntries()

Sub-directories and files


Directory Members GetLastAccessTime() GetLastWriteTime() GetLogicalDrives()

Returns disk drives on the machine in a string

GetParent() Move() SetCreationTime() SetCurrentDirectory()


Directory Members

SetLastAccessTime() SetLastWriteTime()


DirectoryInfo

Provides the same info Directory will But you can create instances

(Not static!)


Path static class

To manage path stuff duh!


UNC Names Paths can refer to a file or just a directory can refer to a relative path can refer to a Universal Naming Convention (UNC)

path for a server and share name Example, all the following are acceptable paths:

"c:\\MyDir\\MyFile.txt" in C# "c:\\MyDir" in C# "MyDir\\MySubdir" in C# "\\\\MyServer\\MyShare" in C#

@“\\<server>\<share>\<relative path>”


using System; using System.IO; class Test { public static void Main() { string path1 = @"c:\temp\MyTest.txt"; string path2 = @"c:\temp\MyTest"; string path3 = @"temp"; if (Path.HasExtension(path1)) { Console.WriteLine("{0} has an extension.", path1); } if (!Path.HasExtension(path2)) { Console.WriteLine("{0} has no extension.", path2); } if (!Path.IsPathRooted(path3)) { Console.WriteLine("The string {0} contains no root information.", path3); } Console.WriteLine("The full path of {0} is {1}.", path3, Path.GetFullPath(path3)); Console.WriteLine("{0} is the location for temporary files.", Path.GetTempPath()); Console.WriteLine("{0} is a file available for use.", Path.GetTempFileName()); Console.WriteLine("\r\nThe set of invalid characters in a path is:"); Console.WriteLine("(Note that the wildcard characters '*' and '?' are not invalid.):"); foreach (char c in Path.InvalidPathChars) { Console.WriteLine(c); } } }

Path class Usage


Public Path Fields

AltDirectorySeparatorChar DirectorySeparatorChar InvalidPathChars PathSeparator VolumeSeparatorChar


Path Methods ChangeExtension() Combine() GetDirectoryName() GetExtension() GetFileName() GetFileNameWithoutExtension() GetFullPath() GetPathRoot() GetTempFileName()


Path Methods cont

GetTempPath() HasExtension() IsPathRooted()


File static class

File’s job is to do file handling Can use it much like a command line


File Methods AppendText () Copy () Create () CreateText () Delete () Exists () GetAttributes() GetCreationTime()


File Methods GetLastAccessTime() GetLastAccessTime() GetLastWriteTime() Move() Open()

Returns a FileStream

OpenRead() OpenText()


File Methods

OpenWrite() SetAttributes() SetCreationTime() SetLastAccessTime() SetLastWriteTime()


FileInfo

Gives much the same info as File Unlike File, you create a an instance

of FileInfo on a filename Gives more information than File


FileInfo

Length Size in bytes

DirectoryName Extension FullName


System.IO

Datatypes and classes for reading from and writing to data streams and files, and other input/output (I/O) functionality.

Throws IOException when required.


Sytem.IO Path static class Directory(static)/DirectoryInfo classes File(static)/FileInfo classes DriveInfo class Registry class IsolatedStorageFileSystem class Stream class

Associated Stream classes FileSystemWatcher class


System.IO namespace BinaryReaderReads primitive data types as binary values in a specific encoding. BinaryWriterWrites primitive types in binary to a stream and supports writing strings in a specific encoding. BufferedStreamAdds a buffering layer to read and write operations on another stream. This class cannot be inherited. DirectoryExposes static methods for creating, moving, and enumerating through directories and subdirectories. DirectoryInfoExposes instance methods for creating, moving, and enumerating through directories and subdirectories. DirectoryNotFoundExceptionThe exception that is thrown when part of a file or directory cannot be found. EndOfStreamExceptionThe exception that is thrown when reading is attempted past the end of a stream. ErrorEventArgsProvides data for the Error event. FileProvides static methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects. FileInfoProvides instance methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects. FileLoadExceptionThe exception that is thrown when a managed assembly is found but cannot be loaded. FileNotFoundExceptionThe exception that is thrown when an attempt to access a file that does not exist on disk fails. FileStreamExposes a Stream around a file, supporting both synchronous and asynchronous read and write operations. FileSystemEventArgsProvides data for the directory events: Changed, Created, Deleted. FileSystemInfoProvides the base class for both FileInfo and DirectoryInfo objects. FileSystemWatcherListens to the file system change notifications and raises events when a directory, or file in a directory,

changes. InternalBufferOverflowExceptionThe exception thrown when the internal buffer overflows. IODescriptionAttributeSets the description visual designers can display when referencing an event, extender, or property. IOExceptionThe exception that is thrown when an I/O error occurs. MemoryStreamCreates a stream whose backing store is memory. PathPerforms operations on String instances that contain file or directory path information. These operations are performed in

a cross-platform manner. PathTooLongExceptionThe exception that is thrown when a pathname or filename is longer than the system-defined maximum

length . RenamedEventArgsProvides data for the Renamed event. StreamProvides a generic view of a sequence of bytes. StreamReaderImplements a TextReader that reads characters from a byte stream in a particular encoding. StreamWriterImplements a TextWriter for writing characters to a stream in a particular encoding. StringReaderImplements a TextReader that reads from a string. StringWriterImplements a TextWriter for writing information to a string. The information is stored in an underlying StringBuilder.TextReaderRepresents a reader that can read a sequential series of characters. TextWriterRepresents a writer that can write a sequential series of characters. This class is abstract.Structures

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File.OpenFileInfo.Open

FileStream Constructoretc.

O’Reily C# Text

BufferedStreamStream

(abstract base class for all streams)NetworkStream

CryptoStream FileStream MemoryStream

IsolatedStorageFileStream

TextReaderTextWriter

StringReaderStringWriter

StreamReaderStreamWriter

BinaryReaderBinaryWriter

text binary


Object Serialization

Ability to write and read object(s) to and from a stream.

Filestream BinaryFormatter

Serialization Deserialization

Serialized objects must be have the [Serializable] attribute

Serialization/Deserialization


public class FileSerialization{ private FileStream fs; private BinaryFormatter bf; private SortedDictionary<uint, Data> DirData; public FileSerialization() { DirData = new SortedDictionary<uint, Data>

{ {100, new Data("Data 1")}, {101, new Data("Data 2")}, {102, new Data("Data 3")}, {103, new Data("Data 4")}, {104, new Data("Data 5")}

}; }…}


public void BinaryFormatWriter(){ try { fs = new FileStream(@"G:\BinaryFormat.bn", FileMode.Create, FileAccess.Write); bf = new BinaryFormatter(); bf.Serialize(fs, DirData); } catch (IOException ioexp) { Console.WriteLine("IOException - {0}", ioexp.Message); } catch (Exception exp) { Console.WriteLine("Exception - {0}",exp.Message); } finally { fs.Close(); Console.WriteLine("BinaryFormatWriter finally"); }}

[Serializable]public class Data{ private string _name; public Data(string name) { _name = name; }}


public void BinaryFormatReader(){ try { fs = new FileStream(@"G:\BinaryFormat.bin", FileMode.Open, FileAccess.Read); bf = new BinaryFormatter(); DirData.Clear(); DirData = (SortedDictionary<uint, Data>)bf.Deserialize(fs); } catch (IOException ioexp) { Console.WriteLine("IOException - {0}", ioexp.Message); } catch (Exception exp) { Console.WriteLine("Exception - {0}", exp.Message); } finally { fs.Close(); Console.WriteLine("BinaryFormatReader finally"); }}


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

namespace FileSerialization_01cs{ class Program { static void Main() { FileSerialization fileSerialize = new FileSerialization(); fileSerialize.BinaryFormatWriter(); fileSerialize.BinaryFormatReader(); Console.ReadLine(); } }


MemoryStream

Like all other streams Data stored in memory

Flushing doesn’t really occur Though still possible

Convenient for having in memory stream behavior

Garbage Collected later


MemoryStream Constructors

Several different ones for different behavior

Can supply the buffer to the stream MemoryStream(byte[], startIndex,

length, writeAble, publiclyVisable) startIndex + length must be less than

the byte array’s length


MemoryStream Constructorsusing System;using System.IO;

class MainClass{ static void Main() { byte[] b = new byte[5]; MemoryStream ms = new MemoryStream(b, 1, 4,true,true); BinaryWriter bw = new BinaryWriter(ms); bw.Write(5); Console.WriteLine(ms.GetBuffer()[1]); // 5 }}

public MemoryStream ( byte[] buffer, int index, int count, bool writable, bool publiclyVisible )



class MainClass{ static void Main() { byte[] b = new byte[5]; MemoryStream ms = new MemoryStream(b, 1, 4,true,true); ms.GetBuffer(); // Legal because publiclyVisable BinaryWriter bw = new BinaryWriter(ms); bw.Write(5); Console.WriteLine(ms.GetBuffer()[1]); // 5 }}



class MainClass{ static void Main() { byte[] b = new byte[5]; MemoryStream ms = new MemoryStream(b, 1, 4, true); BinaryWriter bw = new BinaryWriter(ms); bw.Write(5); // publiclyVisible is false Console.WriteLine(b[1]); // 5 }}



class MainClass{ static void Main() { byte[] b = new byte[5]; MemoryStream ms = new MemoryStream(b, 1, 4); // writeable is true

// publiclyVisible is false BinaryWriter bw = new BinaryWriter(ms); bw.Write(5); Console.WriteLine(b[1]); // 5 }}



class MainClass{ static void Main() { byte[] b = new byte[5]; // lengths and indexes are defaulted MemoryStream ms = new MemoryStream(b, true); BinaryWriter bw = new BinaryWriter(ms);

//PubliclyVisible is false bw.Write(5); Console.WriteLine(b[0]); // 5 }}



class MainClass{ static void Main() { MemoryStream ms = new MemoryStream(); BinaryWriter bw = new BinaryWriter(ms); bw.Write(5); Console.WriteLine(ms.GetBuffer()[0]); // 5 }}


XML

HTML like, but well formed Begin tags and end tags required Only a single root Makes a perfect (well formed) tree

Enforced, unlike HTML Tag names are arbitrary

No tags have any meaning to XML itself


XML Serialization

Save the state of your objects A single object in a single file Single hierarchy Wrap data in a single object Save it away Retrieve it Uses attributes and metadata about

the class


XML Serialization

Visible fields are saved away Fields must have getters and setters Or they can be public

Will take this approach here to save space

Read as a text file Good or bad?


A Student Info Class// Must be public!public class StudentInfo{ public string name = "Dennis Fairclough"; public int age = int.MaxValue; public float gpa = 2.0f; public int IQ = 50; public override bool Equals(object obj) { StudentInfo si = obj as StudentInfo; return this.name == si.name && this.age == si.age && this.IQ == si.IQ; } public override int GetHashCode() {return 0;}}


One Way (Old Way)

Have two separate methods Read() Write()

The methods encrypt in text or binary output Binary much more compact over text Binary much more compact over XML


Newer Way

Allow XML serialization to worry about that stuff for you

Practically hidden from the programmer

System.XML System.XML.Serialization


XMLSerializerclass MainClass{ static void Main() { StudentInfo si = new StudentInfo(); // Text based StreamWriter sw = new StreamWriter("c:\\Temp.xml"); XmlSerializer xs = new XmlSerializer(typeof(StudentInfo)); xs.Serialize(sw, si); sw.Close(); }}


Result<?xml version="1.0" encoding="utf-8" ?> <StudentInfo

xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<name>Dennis Fairclough</name> <age>2147483647</age> <gpa>2</gpa> <IQ>50</IQ> </StudentInfo>


Deserialization

Almost the same as serialization Retrieves the entire object Cast is required

Deserialization returns generic object reference


Deserializationclass MainClass{ static void Main() { StudentInfo si; StreamReader sr = new StreamReader("c:\\Temp.xml"); XmlSerializer xs = new

XmlSerializer(typeof(StudentInfo)); si = (StudentInfo)xs.Deserialize(sr); sr.Close(); Console.WriteLine(si.Equals(new StudentInfo())); // True }}


Collections and XML

Collections are not “strongly typed” object typed

Thus you need to know the underlying types

Use this with XmlArrayItem


XmlArrayItempublic class StudentInfo{ public string name = "Dennis Fairclough"; public int age = int.MaxValue; public float gpa = 2.0f; public int IQ = 50; public override bool Equals(object obj) { StudentInfo si = obj as StudentInfo; return this.name == si.name && this.age == si.age && this.IQ == si.IQ; } public override int GetHashCode() { return 0; } [XmlArrayItem(typeof(int))] public ArrayList items = new ArrayList();}


XmlArrayItem<?xml version="1.0" encoding="utf-8" ?>

<StudentInfo xmlns:xsd=http://www.w3.org/2001/XMLSchema xmlns:xsi="http://www.w3.org/2001/XMLSchema-

instance"> <name>Dennis Fairclough</name> <age>2147483647</age> <gpa>2</gpa> <IQ>50</IQ>

<items> <int>5</int> </items> </StudentInfo>

http://www.w3.org/2001/XMLSchema


XmlArrayItem

Supports inheritance Supports multiple objects


XmlArrayItempublic class StudentInfo{ public string name = "Dennis Fairclough"; public int age = int.MaxValue; public float gpa = 2.0f; public int IQ = 50; public override bool Equals(object obj) { StudentInfo si = obj as StudentInfo; return this.name == si.name && this.age == si.age && this.IQ == si.IQ; } public override int GetHashCode() { return 0; } [XmlArrayItem(typeof(int))] [XmlArrayItem(typeof(string))] public ArrayList items = new ArrayList();}


XmlArrayItem <?xml version="1.0" encoding="utf-8" ?>

<StudentInfo xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<name>Dennis Fairclough</name> <age>2147483647</age> <gpa>2</gpa> <IQ>50</IQ>

<items> <int>5</int> <string>Dennis</string> </items> </StudentInfo>


Inheritancepublic class Top{ public int i;}

public class Bottom : Top{ public int i; // Hides}

public class StudentInfo{ public string name = "Dennis Fairclough"; public int age = int.MaxValue; public float gpa = 2.0f; public int IQ = 50; public override bool Equals(object obj) { StudentInfo si = obj as StudentInfo; return this.name == si.name && this.age == si.age && this.IQ == si.IQ; } public override int GetHashCode() { return 0; } [XmlArrayItem(typeof(Top))] [XmlArrayItem(typeof(Bottom))] public ArrayList items = new ArrayList();}


Inheritanceclass MainClass{ static void Main() { StudentInfo si = new StudentInfo(); Bottom b = new Bottom(); b.i = 5; si.items.Add(b); Top t = new Top(); t.i = 6; si.items.Add(t); // Text based StreamWriter sw = new StreamWriter("c:\\Temp.xml"); XmlSerializer xs = new XmlSerializer(typeof(StudentInfo)); xs.Serialize(sw, si); sw.Close(); }}


Inheritance <?xml version="1.0" encoding="utf-8" ?>

<StudentInfo xmlns:xsd=http://www.w3.org/2001/XMLSchema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <name>Dennis Faiclough</name> <age>2147483647</age> <gpa>2</gpa> <IQ>50</IQ>

<items> <Bottom>

<i>5</i> </Bottom>

<Top> <i>6</i> </Top> </items> </StudentInfo>

http://www.w3.org/2001/XMLSchema


Representing other types XML serialization only supports “primitive” types So how do we serialize other types?

Font Color JPG

Have to convert all fields to “understood” types string int char


Representing other types

public class MyClassWithFont{ private Font font = new Font("courier", 12f); public string FontString { get { return font.Name + '|' + font.Size; } set { font = new Font(value.Split('|')[0], float.Parse(value.Split('|')[1])); } }}

class MainClass{ static void Main() { MyClassWithFont fontClass = new MyClassWithFont(); StreamWriter sw = new StreamWriter("c:\\Temp.xml"); XmlSerializer xs = new XmlSerializer(typeof(MyClassWithFont)); xs.Serialize(sw, fontClass); sw.Close(); }}


Representing other types<?xml version="1.0" encoding="utf-8" ?>

<MyClassWithFont xmlns:xsd= "http://www.w3.org/2001/XMLSchema"

xmlns:xsi= "http://www.w3.org/2001/XMLSchema- instance"> <FontString>Microsoft Sans

Serif|12</FontString> </MyClassWithFont>


Representing other typesclass MainClass{ static void Main() { MyClassWithFont fontClass; StreamReader sr = new StreamReader("c:\\Temp.xml"); XmlSerializer xs = new

XmlSerializer(typeof(MyClassWithFont)); fontClass = xs.Deserialize(sr) as MyClassWithFont; sr.Close(); }}


JPG

Can do with cooperation of streams and XML

Convert JPG to string Actually, almost anything can be

converted to a string


JPG public string ImageToXml { get { MemoryStream ms = new MemoryStream(); Bitmap b = new Bitmap(image); b.Save(ms, ImageFormat.Jpeg); byte[] bytes = ms.GetBuffer(); string ret = Convert.ToBase64String(bytes); b.Dispose(); return ret; } set { byte[] bytes = Convert.FromBase64String(value); MemoryStream ms = new MemoryStream(bytes); image = Image.FromStream(ms); state = State.Printed; } }


Word to the Wise

‘\u0000’ is an illegal XML Character Don’t allow your types to insert it into

the file RTF


Common Dialog Boxes

OpenFileDialog properties methods

SaveFileDialog properties methods


OpenFileDialog OpenFileDialog Constructor Public Properties AddExtension

(inherited from FileDialog)Gets or sets a value indicating whether the dialog box automatically adds an extension to a file name if the user omits the extension.

CheckFileExistsOverridden. Gets or sets a value indicating whether the dialog box displays a warning if the user specifies a file name that does not exist.

CheckPathExists (inherited from FileDialog)Gets or sets a value indicating whether the dialog box displays a warning if the user specifies a path that does not exist.

Container (inherited from Component)Gets the IContainer that contains the Component. DefaultExt (inherited from FileDialog)Gets or sets the default file name extension. DereferenceLinks (inherited from FileDialog)Gets or sets a value indicating whether the dialog box returns the location of the

file referenced by the shortcut or whether it returns the location of the shortcut (.lnk). FileName (inherited from FileDialog) Supported by the .NET Compact Framework. Gets or sets a string containing the file name selected in the file dialog box. FileNames (inherited from FileDialog)Gets the file names of all selected files in the dialog box. Filter (inherited from FileDialog) Supported by the .NET Compact Framework. Gets or sets the current file name filter string, which determines the choices that appear in the "Save as file type" or "Files of

type" box in the dialog box. FilterIndex (inherited from FileDialog) Supported by the .NET Compact Framework. Gets or sets the index of the filter currently selected in the file dialog box. InitialDirectory (inherited from FileDialog) Supported by the .NET Compact Framework. Gets or sets the initial directory displayed by the file dialog box. MultiselectGets or sets a value indicating whether the dialog box allows multiple files to be selected. ReadOnlyCheckedGets or sets a value indicating whether the read-only check box is selected. RestoreDirectory (inherited from FileDialog)Gets or sets a value indicating whether the dialog box restores the current

directory before closing. ShowHelp (inherited from FileDialog)Gets or sets a value indicating whether the Help button is displayed in the file dialog. ShowReadOnlyGets or sets a value indicating whether the dialog box contains a read-only check box. Site (inherited from Component)Gets or sets the ISite of the Component. Title (inherited from FileDialog)Gets or sets the file dialog box title. ValidateNames (inherited from FileDialog)Gets or sets a value indicating whether the dialog box accepts only valid Win32 file

names.

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OpenFileDialog Methods Public Methods CreateObjRef (inherited from MarshalByRefObject)Creates an object that contains all the relevant

information required to generate a proxy used to communicate with a remote object. Dispose (inherited from Component)Overloaded. Releases the resources used by the Component. Equals (inherited from Object) Supported by the .NET Compact Framework. Overloaded. Determines whether two Object instances are equal. GetHashCode (inherited from Object) Supported by the .NET Compact Framework. Serves as a hash function for a particular type, suitable for use in hashing algorithms and data

structures like a hash table. GetLifetimeService (inherited from MarshalByRefObject)Retrieves the current lifetime service object

that controls the lifetime policy for this instance. GetType (inherited from Object) Supported by the .NET Compact Framework. Gets the Type of the current instance. InitializeLifetimeService (inherited from MarshalByRefObject)Obtains a lifetime service object to

control the lifetime policy for this instance. OpenFileOpens the file selected by the user, with read-only permission. The file is specified by the

FileName property. ResetOverridden. See FileDialog.Reset.

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BufferedStream

Wrapper Buffers data Less calls to reads and writes Saves time when needed


Buffer Size

Determined by you via the constructor

4096 bytes is default


Buffer

Only used if needed If write or read is too large, buffer not used Nor created

Otherwise buffering occurs to save time Not designed for switching often between

reads and writes


BufferedStreamusing System.IO;

class MainClass{ static void Main() { BufferedStream bs = new BufferedStream(new MemoryStream()); byte[] b = new byte[4096]; bs.Write(b, 0, b.Length); // Buffer not created or used }}



class MainClass{ static void Main() { BufferedStream bs = new BufferedStream(new MemoryStream()); byte[] b = new byte[4096]; bs.Write(b, 0, b.Length); // Buffer not created bs.Read(b, 0, b.Length); // Buffer still not used }}



class MainClass{ static void Main() { BufferedStream bs = new BufferedStream(new MemoryStream()); byte[] b = new byte[4095]; bs.Write(b, 0, b.Length); // Buffer created }}



class MainClass{ static void Main() { BufferedStream bs = new BufferedStream(new MemoryStream(), 10); byte[] b = new byte[10]; bs.Write(b, 0, b.Length); // Buffer not created or used b = new byte[9]; bs.Write(b, 0, b.Length); }}


Can[whatever]using System;using System.IO;

class MainClass{ static void Main() { BufferedStream bs = new BufferedStream(new MemoryStream(), 10); Console.WriteLine(bs.CanRead); Console.WriteLine(bs.CanWrite); Console.WriteLine(bs.CanSeek); Console.WriteLine(bs.Length); Console.WriteLine(bs.Position); }}


BufferedStreamusing System;using System.IO;

class MainClass{ static void Main() { BufferedStream bs = new BufferedStream(new MemoryStream(), 10); bs.Close(); Console.WriteLine(bs.CanRead); Console.WriteLine(bs.CanWrite); Console.WriteLine(bs.CanSeek); // Following throws// Console.WriteLine(bs.Length);// Console.WriteLine(bs.Position); }}


String IO

StreamReader and StreamWriter Strings in memory use string reader


StringBuilder

C# mutable string Behaves like C++ strings Can append, remove, etc. Mainly a wrapper of a string that

gives dynamic behavior


StringReader and StringWriter

Used for reading/writing from strings Text

Duh


StringReader

Reads string objects StringBuilder ToString() converts to a

string Fascinating I’m sure


StringReaderusing System;using System.Diagnostics;using System.IO;

class MainClass{ static void Main() { StringReader sr = new StringReader("xValue =

25"); char[] buf = new char[2]; sr.Read(buf, 1, 1); Debug.Assert(buf[1] == 'x'); }}


StringWriter

Uses StringBuilder Needs a mutable string


StringWriterusing System;using System.Diagnostics;using System.Text;using System.IO;

class MainClass{ static void Main() { StringBuilder sb = new StringBuilder(); StringWriter sw = new StringWriter(sb); sw.Write("This, that"); Debug.Assert(sb.ToString() == "This, that"); }}


A Dumb Slideusing System;using System.Diagnostics;using System.Text;using System.IO;

class MainClass{ static void Main() { StreamWriter sw = new StreamWriter("moo"); sw.Write("SomeDumbSlide"); sw.Close(); StreamReader sr = new StreamReader("moo"); string s = sr.ReadToEnd(); Debug.Assert(s == "SomeDumbSlide"); sr.Close(); }}


What did you learn?

??

streams & file input/output basics c#.net development version 1.1

Documents

instance methods

static methods

file class

fileinfo class

directoryinfo class

stream cleanup

stream reader

stream writer