NET.C#.0 8. Managinge the File system

ability to interact with the file system:
creation of new

files
copying files
deleting files
moving files from one directory to another

The classes that are used to browse around the file system and perform the operations are File, FileInfo, Directory, DirectoryInfo, FileSystemInfo, Path

FileSystemInfo – Base class that represents any file system object

FileInfo and File – These classes represent a file on the file system

DirectoryInfo and Directory – These classes represent a folder on the file system

Path – contains static method that you can use to manipulate pathnames

only static methods. You use these classes by supplying the

path to the appropriate file system object. If you only want to do one operation on a folder or file then using these classes is more efficient, because it saves the overhead of instantiating a .NET class

DirectoryInfo and FileInfo implement the same public methods as Directory and File, but the members of these classes are not static. You need to instantiate these classes before each instance is associated with a particular folder or file. This means that these classes are more efficient if you’re performing multiple operations using the same object, because they read in the authentication and other information for the appropriate file system object on construction, and then do not need to read that information again.

string sourceFile = "...";
string destFile = "...";
bool overwrite = false;
File.Copy(sourceFile, destFile, overwrite);

string filePath = "...";
FileInfo file = new FileInfo(filePath);
string destPath = "...";
file.CopyTo(destPath);

//Copying file
FileInfo myFile = new FileInfo(@”C:\Program Files\ReadMe.txt”);
myFile.CopyTo(@”D:\Copies\ReadMe.txt”);

//The same effect
File.Copy(@”C:\Program Files\ReadMe.txt”,@”D:\Copies\ReadMe.txt”);

file system object using the following methods:
// displays the creation

time of a file, then changes it and
// displays it again
FileInfo test = new FileInfo(@”C:\My Documents\MyFile.txt”);
Console.WriteLine(test.Exists.ToString());
Console.WriteLine(test.CreationTime.ToString());
test.CreationTime = new DateTime(2001, 1, 1, 7, 30, 0);
Console.WriteLine(test.CreationTime.ToString());

allows you to browse around the file system, and view

the creation time, last access time, last write time, and size of files

standard C# Windows application and add the
various text boxes

and the list boxes:

textBoxInput

textBoxFolder

buttonDisplay

buttonUp

listBoxFiles

listBoxFolders

textBoxFileName

textBoxCreationTime

textBoxFileSize

textBoxLastAccessTime

textBoxLastWriteTime

Step 2. Indicate that we will be using the System.IO namspace:

Using System.IO;

the main form:
Step 4. Add event handlers for the user-generated

events:

public partial class Form1 : Form
{
private string currentFolderPath;

Stores the path of the folder whose contants are displayed in the list box

User clicks the Display button

User clicks on a file name in the Files list box

User clicks on a folder name in the Folders list box

User clicks on the Up button

all the work

//clear the contents of all controls
protected void

ClearAllFields()
{
listBoxFolders.Items.Clear();
listBoxFiles.Items.Clear();
textBoxFolder.Text = “”;
textBoxFileName.Text = “”;
textBoxCreationTime.Text = “”;
textBoxLastAccessTime.Text = “”;
textBoxLastWriteTime.Text = “”;
textBoxFileSize.Text = “”;
}

all the work

//Display information for a given file in the

text boxes
protected void DisplayFileInfo(string fileFullName)
{
FileInfo theFile = new FileInfo(fileFullName);
if (!theFile.Exists)
throw new FileNotFoundException(“File not found: “ + fileFullName);
textBoxFileName.Text = theFile.Name;
textBoxCreationTime.Text = theFile.CreationTime.ToLongTimeString();
textBoxLastAccessTime.Text = theFile.LastAccessTime.ToLongDateString();
textBoxLastWriteTime.Text = theFile.LastWriteTime.ToLongDateString();
textBoxFileSize.Text = theFile.Length.ToString() + “ bytes”;
}

all the work

//Display the contents of a given folder in

the two list boxes
protected void DisplayFolderList(string folderFullName)
{
DirectoryInfo theFolder = new DirectoryInfo(folderFullName);
if (!theFolder.Exists)
throw new DirectoryNotFoundException(“Folder not found: “
+ folderFullName);
ClearAllFields();
textBoxFolder.Text = theFolder.FullName;
currentFolderPath = theFolder.FullName;
// list all subfolders in folder
foreach(DirectoryInfo nextFolder in theFolder.GetDirectories())
listBoxFolders.Items.Add(nextFolder.Name);
// list all files in folder
foreach(FileInfo nextFile in theFolder.GetFiles())
listBoxFiles.Items.Add(nextFile.Name);
}

all the work

//Display button handler
protected void OnDisplayButtonClick(object sender, EventArgs e)
{

string folderPath = textBoxInput.Text;
DirectoryInfo theFolder = new DirectoryInfo(folderPath);
if (theFolder.Exists)
{ DisplayFolderList(theFolder.FullName);return;}
FileInfo theFile = new FileInfo(folderPath);
if (theFile.Exists)
{ DisplayFolderList(theFile.Directory.FullName);
int index = listBoxFiles.Items.IndexOf(theFile.Name);
listBoxFiles.SetSelected(index, true);
return;
}
throw new FileNotFoundException(“There is no file or folder with “
+ “this name: “ + textBoxInput.Text);
}

all the work

//Event handler that is called when an item

in the Files list
//box is selected
protected void OnListBoxFilesSelected(object sender, EventArgs e)
{
try
{
string selectedString = listBoxFiles.SelectedItem.ToString();
string fullFileName = Path.Combine(currentFolderPath,
selectedString);
DisplayFileInfo(fullFileName);
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}

all the work

//Event handler for the selection of a folder

in the Folder list
protected void OnListBoxFoldersSelected(object sender, EventArgs e)
{
try
{
string selectedString = listBoxFolders.SelectedItem.ToString();
string fullPathName = Path.Combine(currentFolderPath, selectedString);
DisplayFolderList(fullPathName);
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}

all the work

//Event handler for Up button
protected void OnUpButtonClick(object sender,

EventArgs e)
{
try
{
string folderPath = new FileInfo(currentFolderPath).DirectoryName;
DisplayFolderList(folderPath);
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}

in principle very simple; however, it is not done through

the DirectoryInfo or FileInfo objects. it is done through a number of classes that represent a generic concept called a stream.

A stream is an object used to transfer data.
The data can be transferred in one of two directions:
If the data is being transferred from some outside source into your program, then we talk about reading from the stream.
If the data is being transferred from your program to some outside source, then we talk about writing to the stream.

writing binary data in a binary file.
However, you can also

use it to read from or write to any file.
StreamReader and StreamWriter — These classes are designed specifically for reading from and writing to text files.stream.

(ASCII, Unicode, UTF8)
StreamReader sr = new StreamReader(@”c:\Documents\ReadMe.txt”, Encoding.UTF8);
//
FileStream fs =

new FileStream(@”C:\My Documents\ReadMe.txt”,
FileMode.Open, FileAccess.Read, FileShare.None);
StreamReader sr = new StreamReader(fs);

StreamReader. The simplest constructor takes just a file name

StreamWriter(chosenFile, false,
Encoding.Unicode);
foreach (string line in textBoxContents.Lines)
sw.WriteLine(line);
sw.Close();

}

StreamWriter. Write each line of the text box to a StreamWriter steram

new FileStream(filePath);
...
BinaryReader reader = new BinaryReader(file);
...
BinaryWriter writer = new BinaryWriter(file);
При

построении объектам BinaryReader и BinaryWriter предоставляется поток, подключенный к источнику данных, из которого нужно читать или в который необходимо писать

Когда использование объектов BinaryReader или BinaryWriter завершено, необходимо вызвать метод Close, чтобы флешировать поток и освободить любые ресурсы, связанные с потоком

Необходимо также закрыть объект FileStream, предоставляющий данные для объектов BinaryReader и BinaryWriter.

dataCollection = { 1, 4, 6, 7, 12, 33, 26,

98, 82, 101 };
FileStream destFile = new FileStream(
destinationFilePath,
FileMode.Create
FileAccess.Write);
BinaryWriter writer = new BinaryWriter(destFile);
foreach (byte data in dataCollection)
{
writer.Write(data);
}
writer.Close();
destFile.Close();

Закрыть оба потока для сброса данных в файл

Запись каждого байта в поток

Коллекция байт

Создание объекта FileStream для взаимодействия с файловой системой

Создание объекта BinaryWriter, передавая объект FileStream как параметр

sourceFile = new FileStream(

sourceFilePath,
FileMode.Open
FileAccess.Read);
BinaryReader reader = new BinaryReader(sourceFile);
int position = 0;
int length = (int)reader.BaseStream.Length;
byte[] dataCollection = new byte[length];
int returnedByte;
while ((returnedByte = reader.Read()) != -1)
{
dataCollection[position] = (byte)returnedByte;
position += sizeof(byte);
}
reader.Close();
sourceFile.Close();

Закрытие потоков для освобождения всех дескрипторов файлов

Создание объекта FileStream для взаимодействия с файловой системой

Создание объекта BinaryWriter, передавая объект FileStream как параметр

Если операции чтения из файла или записи в файл генерируют исключение, следует убедиться, что потоки и дескрипторы файлов освобождены

classes
string filePath = "...";
FileStream file = new FileStream(filePath );
...
StreamReader reader

= new StreamReader(file);
...
StreamWriter writer = new StreamWriter(file);

Close()

Peek()

Read()

ReadBlock()

EndOfStream

ReadLine()

ReadToEnd()

Create a FileStream object so that you can interact with

the file system
FileStream sourceFile = new FileStream(
sourceFilePath, // Pass in the source file path.
FileMode.Open, // Open an existing file.
FileAccess.Read);// Read an existing file.
StreamReader reader = new StreamReader(sourceFile);
StringBuilder fileContents = new StringBuilder();
// Check to see if the end of the file has been reached.
while (reader.Peek() != -1)
{
// Read the next character.
fileContents.Append((char)reader.Read());
}
// Store the file contents in a new string variable.
string data = fileContents.ToString();
// Always close the underlying streams release any file handles.
reader.Close();
sourceFile.Close();

data;
// Create a FileStream object so that you can
//

interact with the file system.
FileStream sourceFile = new FileStream(
sourceFilePath, // Pass in the source file path.
FileMode.Open, // Open an existing file.
FileAccess.Read);// Read an existing file.
StreamReader reader = new StreamReader(sourceFile);
// Read the entire file into a single string variable.
data = reader.ReadToEnd();
// Always close the underlying streams release any file handles.
reader.Close();
sourceFile.Close();

Класс StreamReader

data = "Hello, this will be written in plain text";
//

Create a FileStream object so that you can interact with the file
// system.
FileStream destFile = new FileStream(
destinationFilePath, // Pass in the destination path.
FileMode.Create, // Always create new file.
FileAccess.Write); // Only perform writing.
// Create a new StreamWriter object.
StreamWriter writer = new StreamWriter(destFile);
// Write the string to the file.
writer.WriteLine(data);
// Always close the underlying streams to flush the data to the file
// and release any file handles.
writer.Close();
destFile.Close();

StreamWriter