Input/Output with .NET Framework Class Library pps

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Input/Output with

m NET Framework Class Library

Pham Minh Tuan

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a a dung trinh bay

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a the File System m Nhu cầu: „ Làm sao biết được trên hệ thống có những ổ đĩa nào?

„ Làm sao lấy được danh sách tập tin và thư mục con của một thư mục nào đó?

„ Làm sao truy xuất được các thuộc tính của mội tập tin, thư mục?

„ Làm sao giám sát được sự thay đổi của một tập

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a Navigating the File System | Drivelnfo class Thuộc tính Name Description AvailablePreeSpace |Gets the amount of available space on the drive The amount might DriveFormat Drive Type isReady Name RootDirectory TotalPreeSpace Totaisize VobhbumeLabel

be different from the amount returned by TotalFreeSpace (described later in this table), depending on disk quotas

Gets the format of the drive, such as NIFS or FAT32

Gets the type of drive in the form of the DriveType enumeration (which is described in the following section)

Gets the status of the drive, indicating whether it is ready to be accessed

Gets the name of the drive

Gets a Directoryinfo object that represents the root directory of the

drive |

Gets the total amount of free space on the drive Gets the total size of the drive

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Navigating the File System

Drivel nfo class

DriveType enum

Name Description

CDRom An optical drive It can be CD-ROM, DVD, and so on

Fixed A fixed disk

Network A network mapped drive

NoRootDirectory |A drive that does not have a root directory

Ram ARAM drive

Removable A drive that has removable media

Unknown The drive could not be determined

Phương thức Name Description

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a Navigating the File System | FileSystemI|nfo class Thuộc tính Name Description

Attributes Gets or sets FileAttributes of the current file or directory

CreationTime |Gets or sets the time that the current file or directory was created Exists Determines whether the file or directory exists

Extension Gets a string representation of the extension part of the file or directory PullName Gets the full path to the file or directory

LastAccessTime |Gets or sets the time the file or directory was accessed LastWriteTime |Gets or sets the time the file or directory was last written to

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a Navigating the File System

FileSystemI|nfo class Phương thức

Name (|Description

Delete \Removes the file or directory from the file system

Refresh \Updates the data in the class with the most current information from the file

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a Navigating the File System

Directoryl nfo class Thuộc tính

Name Description

Parent \Gets the Directoryinfo object for the parent directory of the

current directory in the directory hierarchy

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ae the File System =» Directorylnfo class Phương thức Name Description Create Creates the directory described in the current Lirectorylnfo object

CreateSubdirectory |Creates a new directory as a child directory of the current directory in the directory hierarchy

GetDirectories Retrieves an array of Directoryinfo objects that represent subdirectories of the current directory Get Files Retrieves an array of File/nyfo objects that represent

all the files in the current directory

GethileSysteminjfos |Retrieves an array of FileSystemlnfo objects that represent both files and subdirectories in the current directory

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Navigating the File System

Filelnfo class

Thuộc tính

Name Description

Lirectory Gets the Directory/nfo object that represents the directory

that this file 1s stored within

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a Navigating the File System | Filelnfo class Phương thức Name Description Append Text |Creates a new Stream Writer that will allow appending text to the file CapyTo Create CreateText Decrypt Open Write Replace

Makes a copy of the file in a new location

Creates a file based on the current file information

Creates a new Stream Writer and a new file for writing text Decrypts a file that was encrypted by the current user

Encrypts a file so that only the current user can decrypt the information within the file

Moves the file to a new location

Opens the file with specific privileges (read, read/write, and so on) Opens the file with read-only access

Opens the file and returns a Stream Reader to allow reading of text within the file

Opens the file with write-only access

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ae the File System =» Path class Phương thức Combine GetlDirectoryName Crethxtension GethileName Cret hile Name WithoutEkxtension GethullPath Description

Takes a path and returns a new path with the file name's extension changed (Note that only the path string

changes, not the actual file name extension.) Combines two compatible path strings

Returns the name of the directory in the specified path Returns the name of the file extension in the specified path

Returns the name of the file in the specified path

Returns the file name without the extension in the

specified path

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ae the File System =» Path class Phương thức CretPathRoot CetRandomPileName GetTempPileName GetTempPath HasHxtension isPathRooted

Returns the root directory name in the specified path

Generates arandom file name

Generates a temporary file in the file system and returns the full path to the file

Returns the path to the temporary file directory for the

current user or system

Indicates whether a specified path's file name has an extension

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a Navigating the File System | FileSystemWatcher class Thuộc tính Name NmuabieaisingVvemnfs Filter lucludeSubdirectories NotifvPilter Description

Gets or sets whether the watcher object should raise events Normally, it's used to turn on and off the watching ofa directory and/or files

Gets or sets the file filter to use to determine which file changes to monitor A blank filter indicates "all files."

Gets or sets an indicator of whether the watching ofa directory 1s to include subdirectories or only the directory specified in the Path

property

Gets or sets the type of changes to watch for By default, all

changes (creation, deletion, renamed files, and modifications) are notified

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Navigating the File System

FileSystemWatcher class Phương thức

Name Description

WaithorChanged |Synchronous method for watching a directory for changes and for returning a structure that contains all the changes

Su kiện

Name (|Description

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a the File System » Lam sao biết được trên hệ thống có những ổ đĩa

nào?

Drivelnfo[] drives = Drivelnfo.GetDrives(); foreach (Drivelnfo drive in drives)

Console.WriteLine("Drive: {0}", drive.Name); Console.WriteLine("Type: {0}",

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a the File System

„ Làm sao lẫy được danh sách tập tin và thư mục con của một thư mục nào đó?

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a the File System

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a the File System

= Lam sao giam sat được sự thay đổi của một tập tin, thư mục?

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a the File System

Cung cấp tất cả các phương thức cần thiết

cho việc tạo file, xóa file, di chuyển file, sao chep file

Cung cấp tất cả các phương thức cần thiết

cho việc tạo thư mục, xóa thư mục, dị

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ac: and Writing Files

=» Stream class

=» FileStream class

» StreamReader class, StreamWriter class

» BinaryReader class, BinaryWriter class » Memorystream class

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§) Reading and Writing Files | Siream class Thuộc tính Name Description

Can Read Determines whether the stream supports reading CanSeek Determines whether the stream supports seeking CanTimeout Determines whether the stream can time out CanWrite Determines whether the stream can be written to Length Gets the length (in bytes) of the stream

Position Gets or sets the virtual cursor for determining where in the stream the current position is The value of Position cannot be greater than the value of the stream's Length

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P Reading and Writing Files m Siream class Phương thức Name Description

Close Closes the stream and releases any resources associated with tt

Plush Clears any buffers within the stream and forces changes to be written to the underlying system or device

Read Performs a sequential read of a specified number of bytes from the current position and updates the position to the end of the read upon completion of the operation

Read Byte Performs the read of a single byte and updates the position by moving it by one Identical to calling Read to read a single byte

Sets the position within the stream

setLength |Specifies the length of the stream Will truncate the stream if the new length is less than the old length and will expand the stream if the reverse 1s true

Write Writes information to the stream as a number of bytes and updates the current position to reflect the new write position

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§) Reading and Writing Files FileStream class: ké thUfa Stream class Thuộc tính Name Description

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§) Reading and Writing Files

Stream Reader class

Kể thửa TextReader class

Dùng để đọc các file văn bản

Thuộc tính

Name Description

BasesStream Gets the underlying stream that the reader 1s reading Current#xucoding |Gets the current encoding used for the underlying

stream

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§) Reading and Writing Files

Stream Reader class

Phương thức

Name Description

Close Closes the reader and the underlying stream

Peek Returns the next character in the stream without moving the

stream's current position

Read Reads the next set of characters in the stream ReadBlock \Reads the next block of characters in the stream Readiine \Reads the next line of characters in the stream

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ac: and Writing Files

= Doc file van ban

FileStream theFile = File.-Open(@"C:\boot.ini",

FileMode.Open, FileAccess Read);

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§) Reading and Writing Files

StreamWriter class

Kể thửa TextWriter class

Dùng để ghi các file văn bản

Thuộc tính

Name Description

AutoPlush \Gets or sets an indicator that shows whether every call to the Write method should flush changes to the underlying stream

SaseStream |Gets the underlying stream that the reader 1s reading Encoding |Gets the current encoding used for the underlying stream

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§) Reading and Writing Files

StreamWriter class

Phương thức

Name Description

Close Closes the writer and the underlying stream

Write Writes to the stream

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ac: and Writing Files

» Vi du

„ Ghi file văn bản

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ac: and Writing Files

=» BinaryReader class

= Dung dé doc file nhi phan

= Cung cap cac phuong thức có dạng

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ac: and Writing Files » Vi du s Đọc file nhị phân FileStream theFile = File.Coen(Œ@”c:\`somefile.bin”, FileMode.Open); BinaryReader reader = new BinaryReader(theFile) ; long number = reader.Readl nt64();

byte[] bytes = reader.ReadBytes(4) ;

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ac: and Writing Files

=» BinaryWriter class

= Dung dé ghi file nhi phan

= Cung cap cac phương thức Write với nhiêu

dạng tham số khác nhau để ghi nội dung

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ac: and Writing Files

» Vi du

a Ghi file nhi phan

FileStream theFile = File.Open(@"c:\somefile.bin",

FileMode.OpenOrCreate, FileAccess Write);

BinaryWriter writer = new

BIinaryWriter(theFile) ;

lòng number = 100;

byte[] bytes = new byte[] { 10, 20, 50, 100 };

string s= “Toi di hoc’; writer.Write(number);

writer Write(bytes);

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§) Reading and Writing Files MemoryStream class: kế thừa Stream class Thuộc tính Name Description Capacity |Gets or sets the number of bytes allocated for the stream Phương thức Name Description

CetSuffer Retrieves the array of unsigned bytes that were used to create the stream

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ac: and Writing Files

MemoryStream memStrm = new MemoryStream();

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ac: and Writing Files

=» BufferedStream class

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he Streams

= Cho phép nén dữ liệu gốc tối đa là 4GB „ Kiểu nén: GZIP và DEFLATE

'N©-:|© lele ho tro

» GZipStream class

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he Streams

=» GZipStream class

„ KẾ thừa Stream class

« Dùng để nén/giải nén tập tin theo GZIP

=» Neén tap ale

FileStream sourceFile = File OQoenRead(inFilename);

FileStream destFile = File.Create(outFilename) ;

GZipStream compStream = new GZipStream(sourceFile,

CompressionMode.Compress): byte[] Arr = new byte[4096];

int theByte = sourceFile.Read(Arr, 0, 4096);

while(theByte!= 0)

{

compstream.Write(Arr, 0, theByte) ;

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he Streams

=» GZipStream class

= Giai nén tap tin

FileStream sourceFile = File OQoenRead(inFilename) ;

FileStream destFile = File.Create(outFilename) ;

GZipStream compStream = new

GZipStream(sourceFile,

CompressionMode.Decompress) ; byte[] Arr = new byte[4096] ;

int theByte = compStream.Read(Arr, 0, 4096);

while (theByte != 0)

|

destFile.Write(Arr, 0, theByte);

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he Streams =» DeflateStream class

Kêt hợp giữa LZ77 và Huffman

Dùng tương tự như GZipStream class

Cho kích thước nén nhỏ hơn

File nén không thể mở được bằng các

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=

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