Stephens' C# Programming with Visual Studio® 2010 24-Hour Trainer

Using File System Classes

The techniques described in Lesson 29 let you read and write text files. They also demonstrate

techniques that you’ll find useful when you deal with streams other than text files.

Those techniques don’t let you manipulate the file system itself, however. They let you read or

write a file, but they don’t let you rename a file, move a file to a different directory, or delete a file.

This lesson describes file system classes that make these and other common file manipulation

operations easy. In this lesson you learn how to manipulate the file system to rename, move, or

delete files and directories. You also learn how to read or write a text file’s contents all at once

rather than using a

StreamReader.

These classes are in the System.IO namespace so you can make using them in

your code easier by including the directive:

using System.IO;

THE DRIVEINFO CLASS

The DriveInfo class provides information about the system’s drives. Its static GetDrives

function returns an array of

DriveInfo objects describing all of the system’s drives.

Table 30-1 summarizes the

DriveInfo’s most useful properties.

TABLE 301

PROPERTY PURPOSE

AvailableFreeSpace

The total number of bytes available.

DriveFormat

The drive format, as in NTFS or FAT32.

30

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LESSON 30 Using File system Classes

PROPERTY PURPOSE

DriveType

The drive type, as in Fixed or CDRom.

IsReady

True if the drive is ready. A drive must be ready before you can

use the

AvailableFreeSpace, DriveFormat, TotalSize, or

VolumeLabel properties.

Name

The drive’s name, as in C:\.

RootDirectory

A DirectoryInfo object representing the drive’s root directory.

TotalFreeSpace

The number of bytes available, taking quotas into account.

TotalSize

The drive’s total size in bytes.

VolumeLabel

The drive’s label.

Example program ListDrives (found as part of this lesson’s code download and shown in

Figure 30-1) uses the following code to describe the system’s drives.

FIGURE 301

// List the available drives.

private void Form1_Load(object sender, EventArgs e)

{

drivesListBox.DataSource = DriveInfo.GetDrives();

}

// Display information about the selected drive.

private void drivesListBox_SelectedIndexChanged(object sender, EventArgs e)

{

DriveInfo info = (DriveInfo)drivesListBox.SelectedItem;

nameTextBox.Text = info.Name;

rootTextBox.Text = info.RootDirectory.FullName;

typeTextBox.Text = info.DriveType.ToString();

isReadyTextBox.Text = info.IsReady.ToString();

TABLE 301

(continued)

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The DirectoryInfo Class

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351

// See if the drive is ready.

if (info.IsReady)

{

// Display values.

labelTextBox.Text = info.VolumeLabel;

totalSpaceTextBox.Text = info.TotalSize.ToString();

totalFreeTextBox.Text = info.TotalFreeSpace.ToString();

availableFreeTextBox.Text = info.AvailableFreeSpace.ToString();

formatTextBox.Text = info.DriveFormat;

}

else

{

// Clear values that are unavailable.

labelTextBox.Clear();

totalSpaceTextBox.Clear();

totalFreeTextBox.Clear();

availableFreeTextBox.Clear();

formatTextBox.Clear();

}

}

THE DIRECTORYINFO CLASS

The DirectoryInfo class provides information about directories. Table 30-2 summarizes useful

DirectoryInfo methods for manipulating directories.

TABLE 302

METHOD PURPOSE

Create

Creates a new directory. To use this, make a DirectoryInfo object,

passing its constructor the name of the directory to create. Then call

the

Create method.

CreateSubdirectory

Creates a subdirectory inside this directory.

Delete

Deletes the directory. If you pass no parameters to this method, it

only deletes the directory if it is empty. Alternatively you can pass it

a Boolean parameter indicating whether you want to delete all of the

directory’s files and subdirectories.

GetDirectories

Returns the directory’s immediate subdirectories. Optionally you can

include a search string to select particular subdirectories.

GetFiles

Returns the directory’s files. Optionally you can include a search string

to select particular files.

MoveTo

Moves the directory to a new path.

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LESSON 30 Using File system Classes

The DirectoryInfo class also provides a few useful properties, which are summarized in Table 30-3.

TABLE 303

PROPERTY PURPOSE

Attributes

The directory’s attributes, such as Compressed, Hidden, or System.

CreationTime

The time at which the directory was created.

Exists

Returns True if the directory actually exists.

FullName

Gives the directory’s fully qualified path.

LastAccessTime

The time at which the directory was last accessed.

LastWriteTime

The time at which the directory was last written.

Name

The directory’s name without the path.

Parent

A DirectoryInfo representing this directory’s parent directory.

Root

The directory’s file system root.

Example program UseDirectoryInfo (found in this lesson’s code download) uses a DirectoryInfo

object to display information about directories.

THE DIRECTORY CLASS

The Directory class provides static methods for manipulating directories (see Table 30-4). For

simple tasks these are sometimes easier to use than the comparable

DirectoryInfo class methods

because you don’t need to create a

DirectoryInfo object to use them.

TABLE 304

METHOD PURPOSE

CreateDirectory

Creates the directory and any missing directories in its path up to the root.

Delete

Deletes a directory.

Exists

Returns true if the directory exists.

GetCreationTime

Returns the time at which the file was created.

GetDirectories

Returns a directory’s subdirectories.

GetDirectoryRoot

Returns the directory’s root.

GetFiles

Returns a directory’s files, optionally looking for files matching a pattern.

GetLastAccessTime

Returns the time at which a directory was last accessed.

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