Framework Classes

The System.IO namespace provides several classes for working with the file system. The following sections describe the properties, methods, and events provided by these classes.

FileSystem

The FileSystem class provides shared methods for working with the file system at a large scale. The following table describes its most useful properties and methods.

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Property or Method	Purpose
CombinePath	Combines a base path with a relative child path and returns the resulting path. For example, the statement FileSystem .CombinePath(“C:\Someplace\Lost”, “..\Else”) returns C:\Someplace\Else.
CopyDirectory	Copies a directory and its contents to a new location. A parameter indicates whether you want to overwrite existing files that have the same names.
CopyFile	Copies a file to a new location, possibly overwriting an existing file.
CreateDirectory	Creates a new directory.
DeleteDirectory	Deletes an existing directory. Parameters indicate whether the method should recursively delete the directory’s contents and whether the deleted files should be placed in the Recycle Bin or deleted permanently.
DeleteFile	Deletes a file. A parameter indicates whether the file should be placed in the Recycle Bin or deleted permanently.
DirectoryExists	Returns True if the specified directory exists.
FileExists	Returns True if the specified file exists.
FindInFiles	Returns a collection holding names of files that contain a search string.
GetDirectories	Returns a read-only collection of strings giving the subdirectories within a specific directory. Parameters indicate whether the method should recursively search the subdirectories and whether the routine should allow wildcards.
GetDirectoryInfo	Returns a DirectoryInfo object representing a directory. Note that the directory need not exist yet. For example, you can create a DirectoryInfo object and then use its Create method to create the directory.
GetDriveInfo	Returns a DriveInfo object representing a drive.
GetFileInfo	Returns a FileInfo object representing a file. Note that the file need not exist yet. For example, you can create a FileInfo object and then use its Create method to create the file.
GetFiles	Returns a read-only collection of strings giving the names of files within a specific directory. Parameters indicate whether the method should recursively search the subdirectories and whether the routine should allow wildcards.
GetName	Returns the name portion of a file path.
GetParentPath	Returns a directory’s parent directory path.
GetTempFileName	Creates a uniquely named empty file and returns its full path.
MoveDirectory	Moves a directory to a new parent directory. A parameter indicates whether you want to overwrite existing files with the same names.
MoveFile	Moves a file to a new directory. Parameters indicate whether the file should overwrite an existing file at the new location.
OpenTextFieldParser	Returns a TextFieldParser for a file. A TextFieldParser makes it easy to read fields from a delimited file or from a file with fixed-width field columns.
OpenTextFileReader	Returns a StreamReader attached to a file.
OpenTextFileWriter	Returns a StreamWriter attached to a file. A parameter indicates whether the StreamWriter should append to the file or create a new file.
ReadAllBytes	Returns a file’s contents as an array of bytes.
ReadAllText	Returns a file’s contents as a string.
RenameDirectory	Changes a directory’s name within its current parent directory.
RenameFile	Changes a file’s name within its current directory.
WriteAllBytes	Writes a byte array into a file. A parameter indicates whether the method should append the bytes to the file or create a new file.
WriteAllText	Writes a string into a file. A parameter indicates whether the method should append the string to the file or create a new file.

Directory

The Directory class provides shared methods for working with directories. The following table summarizes its shared methods.

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Method	Purpose
CreateDirectory	Creates all of the directories along a path.
Delete	Deletes a directory and its contents. It can recursively delete all subdirectories.
Exists	Returns True if the path points to an existing directory.
GetCreationTime	Returns a directory’s creation date and time.
GetCreationTimeUtc	Returns a directory’s creation date and time in Coordinated Universal Time (UTC).
GetCurrentDirectory	Returns the application’s current working directory.
GetDirectories	Returns an array of strings holding the fully qualified names of a directory’s subdirectories.
GetDirectoryRoot	Returns the directory root for a path, which need not exist (for example, C:\).
GetFiles	Returns an array of strings holding the fully qualified names of a directory’s files.
GetFileSystemEntries	Returns an array of strings holding the fully qualified names of a directory’s files and subdirectories.
GetLastAccessTime	Returns a directory’s last access date and time.
GetLastAccessTimeUtc	Returns a directory’s last access date and time in UTC.
GetLastWriteTime	Returns the date and time when a directory was last modified.
GetLastWriteTimeUtc	Returns the date and time when a directory was last modified in UTC.
GetLogicalDrives	Returns an array of strings listing the system’s logical drives as in A:\. The list includes drives that are attached. For example, it lists an empty floppy drive and a connected flash disk but doesn’t list a flash disk after you disconnect it.
GetParent	Returns a DirectoryInfo object representing a directory’s parent directory.
Move	Moves a directory and its contents to a new location on the same disk volume.
SetCreationTime	Sets a directory’s creation date and time.
SetCreationTimeUtc	Sets a directory’s creation date and time in UTC.
SetCurrentDirectory	Sets the application’s current working directory.
SetLastAccessTime	Sets a directory’s last access date and time.
SetLastAccessTimeUtc	Sets a directory’s last access date and time in UTC.
SetLastWriteTime	Sets a directory’s last write date and time.
SetLastWriteTimeUtc	Sets a directory’s last write date and time in UTC.

File

The File class provides shared methods for working with files. The following table summarizes its most useful shared methods.

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Method	Purpose
AppendAllText	Adds text to the end of a file, creating it if it doesn’t exist, and then closes the file.
AppendText	Opens a file for appending UTF-8 encoded text and returns a StreamWriter attached to it.
Copy	Copies a file.
Create	Creates a new file and returns a FileStream attached to it.
CreateText	Creates or opens a file for writing UTF-8 encoded text and returns a StreamWriter attached to it.
Delete	Permanently deletes a file.
Exists	Returns True if the specified file exists.
GetAttributes	Gets a file’s attributes. This is a combination of flags defined by the FileAttributes enumeration, which defines the values Archive, Compressed, Device, Directory, Encrypted, Hidden, Normal, NotContextIndexed, Offline, ReadOnly, ReparsePoint, SparseFile, System, and Temporary.
GetCreationTime	Returns a file’s creation date and time.
GetCreationTimeUtc	Returns a file’s creation date and time in UTC.
GetLastAccessTime	Returns a file’s last access date and time.
GetLastAccessTimeUtc	Returns a file’s last access date and time in UTC.
GetLastWriteTime	Returns a file’s last write date and time.
GetLastWriteTimeUtc	Returns a file’s last write date and time in UTC.
Move	Moves a file to a new location.
Open	Opens a file and returns a FileStream attached to it. Parameters let you specify the mode (Append, Create, CreateNew, Open, OpenOrCreate, or Truncate), access (Read, Write, or ReadWrite), and sharing (Read, Write, ReadWrite, or None) settings.
OpenRead	Opens a file for reading and returns a FileStream attached to it.
OpenText	Opens a UTF-8 encoded text file for reading and returns a StreamReader attached to it.
OpenWrite	Opens a file for writing and returns a FileStream attached to it.
ReadAllBytes	Returns a file’s contents in an array of bytes.
ReadAllLines	Returns a file’s lines in an array of strings.
ReadAllText	Returns a file’s contents in a string.
Replace	This method takes three file paths as parameters representing a source file, a destination file, and a backup file. If the backup file exists, the method permanently deletes it. It then moves the destination file to the backup file, and moves the source file to the destination file. For example, imagine a program that writes a log file every time it runs. It could use this method to keep three versions of the log: the current log (the method’s source file), the most recent backup (the method’s destination file), and a second backup (the method’s backup file). This method throws an error if either the source or destination file doesn’t exist.
SetAttributes	Sets a file’s attributes. This is a combination of flags defined by the FileAttributes enumeration, which defines the values Archive, Compressed, Device, Directory, Encrypted, Hidden, Normal, NotContextIndexed, Offline, ReadOnly, ReparsePoint, SparseFile, System, and Temporary.
SetCreationTime	Sets a file’s creation date and time.
SetCreationTimeUtc	Sets a file’s creation date and time in UTC.
SetLastAccessTime	Sets a file’s last access date and time.
SetLastAccessTimeUtc	Sets a file’s last access date and time in UTC.
SetLastWriteTime	Sets a file’s last write date and time.
SetLastWriteTimeUtc	Sets a file’s last write date and time in UTC.
WriteAllBytes	Creates or replaces a file, writes an array of bytes into it, and closes the file.
WriteAllLines	Creates or replaces a file, writes an array of strings into it, and closes the file.
WriteAllText	Creates or replaces a file, writes a string into it, and closes the file.

DriveInfo

A DriveInfo object represents one of the computer’s drives. The following table describes the properties provided by this class. The final column in the table indicates whether a drive must be ready for the property to work without throwing an exception. Use the IsReady property to see whether the drive is ready before using those properties.

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Property	Purpose	Must Be Ready?
AvailableFreeSpace	Returns the amount of free space available on the drive in bytes. This value takes quotas into account, so it may not match TotalFreeSpace.	True
DriveFormat	Returns the name of the file system type (such as NTFS or FAT32).	True
DriveType	Returns a DriveType enumeration value indicating the drive type. This value can be CDRom, Fixed, Network, NoRootDirectory, Ram, Removable, or Unknown.	False
IsReady	Returns True if the drive is ready. Many DriveInfo properties are unavailable and raise exceptions if you try to access them while the drive is not ready.	False
Name	Return’s the drive’s name. This is the drive’s root name as in A:\ or C:\.	False
RootDirectory	Returns a DirectoryInfo object representing the drive’s root directory. See the section “DirectoryInfo” later in this appendix for more information.	False
TotalFreeSpace	Returns the total amount of free space on the drive in bytes.	True
TotalSize	Returns the total amount of space on the drive in bytes.	True
VolumeLabel	Gets or sets the drive’s volume label.	True

DirectoryInfo

A DirectoryInfo object represents a directory. The following table summarizes its most useful properties and methods.

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Property or Method	Purpose
Attributes	Gets or sets flags from the FileAttributes enumeration for the directory. These flags can include Archive, Compressed, Device, Directory, Encrypted, Hidden, Normal, NotContent?Indexed, Offline, ReadOnly, ReparsePoint, SparseFile, System, and Temporary.
Create	Creates the directory. You can create a DirectoryInfo object, passing its constructor the fully qualified name of a directory that doesn’t exist. You can then call the object’s Create method to create the directory.
CreateSubdirectory	Creates a subdirectory within the directory and returns a DirectoryInfo object representing it. The subdirectory’s path must be relative to the DirectoryInfo object’s directory but can contain intermediate subdirectories. For example, the statement dir_info.CreateSubdirectory(“Tools\ Bin”) creates the Tools subdirectory and the Bin directory inside that.
CreationTime	Gets or sets the directory’s creation time.
CreationTimeUtc	Gets or sets the directory’s creation time in UTC.
Delete	Deletes the directory if it is empty. A parameter lets you tell the object to delete its contents, too, if it isn’t empty.
Exists	Returns True if the directory exists.
Extension	Returns the extension part of the directory’s name. Normally, this is an empty string for directories.
FullName	Returns the directory’s fully qualified path.
GetDirectories	Returns an array of DirectoryInfo objects representing the directory’s subdirectories. An optional parameter gives a pattern to match. This method does not recursively search the subdirectories.
GetFiles	Returns an array of FileInfo objects representing files inside the directory. An optional parameter gives a pattern to match. This method does not recursively search subdirectories.
GetFileSystemInfos	Returns a strongly typed array of FileSystemInfo objects representing subdirectories and files inside the directory. The items in the array are DirectoryInfo and FileInfo objects, both of which inherit from FileSystemInfo. An optional parameter gives a pattern to match. This method does not recursively search subdirectories.
LastAccessTime	Gets or sets the directory’s last access time.
LastAccessTimeUtc	Gets or sets the directory’s last access time in UTC.
LastWriteTime	Gets or sets the directory’s last write time.
LastWriteTimeUtc	Gets or sets the directory’s last write time in UTC.
MoveTo	Moves the directory and its contents to a new path.
Name	Returns the directory’s name without the path information.
Parent	Returns a DirectoryInfo object representing the directory’s parent. If the directory is its file system’s root (for example, C:\), this returns Nothing.
Refresh	Refreshes the DirectoryInfo object’s data. For example, if the directory has been accessed since the object was created, you must call Refresh to load the new LastAccessTime value.
Root	Returns a DirectoryInfo object representing the root of the directory’s file system.
ToString	Returns the directory’s fully qualified path and name.

FileInfo

A FileInfo object represents a file. The following table summarizes its most useful properties and methods.

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Property or Method	Purpose
AppendText	Returns a StreamWriter that appends text to the file.
Attributes	Gets or sets flags from the FileAttributes enumeration for the file. These flags can include Archive, Compressed, Device, Directory, Encrypted, Hidden, Normal, NotContentIndexed, Offline, ReadOnly, ReparsePoint, SparseFile, System, and Temporary.
CopyTo	Copies the file and returns a FileInfo object representing the new file. A parameter lets you indicate whether the copy should overwrite an existing file if it already exists. If the destination path is relative, it is relative to the application’s current directory, not to the FileInfo object’s directory.
Create	Creates the file and returns a FileStream object attached to it. For example, you can create a FileInfo object passing its constructor the name of a file that doesn’t exist. Then you can call the Create method to create the file.
CreateText	Creates the file and returns a StreamWriter attached to it. For example, you can create a FileInfo object passing its constructor the name of a file that doesn’t exist. Then you can call the CreateText method to create the file.
CreationTime	Gets or sets the file’s creation time.
CreationTimeUtc	Gets or sets the file’s creation time in UTC.
Delete	Deletes the file.
Directory	Returns a DirectoryInfo object representing the file’s directory.
DirectoryName	Returns the name of the file’s directory.
Exists	Returns True if the file exists.
Extension	Returns the extension part of the file’s name including the period. For example, the extension for game.txt is .txt.
FullName	Returns the file’s fully qualified path and name.
IsReadOnly	Returns True if the file is marked read-only.
LastAccessTime	Gets or sets the file’s last access time.
LastAccessTimeUtc	Gets or sets the file’s last access time in UTC.
LastWriteTime	Gets or sets the file’s last write time.
LastWriteTimeUtc	Gets or sets the file’s last write time in UTC.
Length	Returns the number of bytes in the file.
MoveTo	Moves the file to a new location. If the destination uses a relative path, it is relative to the application’s current directory, not to the FileInfo object’s directory. When this method finishes, the FileInfo object is updated to refer to the file’s new location.
Name	The file’s name without the path information.
Open	Opens the file with different mode (Append, Create, CreateNew, Open, OpenOrCreate, or Truncate), access (Read, Write, or ReadWrite), and sharing (Read, Write, ReadWrite, or None) settings. This method returns a FileStream object attached to the file.
OpenRead	Returns a read-only FileStream attached to the file.
OpenText	Returns a StreamReader with UTF-8 encoding attached to the file for reading.
OpenWrite	Returns a write-only FileStream attached to the file.
Refresh	Refreshes the FileInfo object’s data. For example, if the file has been accessed since the object was created, you must call Refresh to load the new LastAccessTime value.
Replace	Replaces a target file with this one, renaming the old target as a backup copy. If the backup file already exists, it is deleted and replaced with the target. You can use this method to save backups of logs and other periodically updated files.
ToString	Returns the file’s fully qualified name.

FileSystemWatcher

The FileSystemWatcher class lets an application watch for changes to a file or directory. The following table summarizes its most useful properties.

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Property	Purpose
EnableRaisingEvents	Determines whether the component is enabled. Note that this property is False by default, so the watcher will not raise any events until you set it to True.
Filter	Determines the files for which the watcher reports events. You cannot watch for multiple file types as in *.txt and *.dat. Instead, use multiple FileSystemWatchers. If you like, you can use AddHandler to make all of the FileSystemWatchers use the same event handlers.
IncludeSubdirectories	Determines whether the object watches subdirectories within the main path.
InternalBufferSize	Determines the size of the internal buffer. If the watcher is monitoring a very active directory, a small buffer may overflow.
NotifyFilter	Determines the types of changes that the watcher reports. This is a combination of values defined by the Notify?Filters enumeration and can include the values Attributes, CreationTime, DirectoryName, FileName, LastAccess, LastWrite, Security, and Size.
Path	Determines the path to watch.

The following table summarizes the FileSystemWatcher class’s two most useful methods.

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Method	Purpose
Dispose	Releases resources used by the object.
WaitForChanged	Synchronously waits for a change to the target file or directory.

The following table summarizes the class’s events.

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Name	Description
Changed	A file or subdirectory has changed.
Created	A file or subdirectory was created.
Deleted	A file or subdirectory was deleted.
Error	The watcher’s internal buffer overflowed.
Renamed	A file or subdirectory was renamed.

Path

The Path class provides shared properties and methods that you can use to manipulate paths. The fol-lowing table summarizes its most useful public properties.

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Property	Purpose
AltDirectorySeparatorChar	Returns the alternate character used to separate directory levels in a hierarchical path (typically, /).
DirectorySeparatorChar	Returns the character used to separate directory levels in a hierarchical path (typically, \ ,as in C:\Tests\Billing\ 2005q2.dat).
InvalidPathChars	Returns a character array that holds characters that are not allowed in a path string. Typically, this array will include characters such as “, <, >, and |, as well as nonprintable characters such as those with ASCII values between 0 and 31.
PathSeparator	Returns the character used to separate path strings in environment variables (typically, ;).
VolumeSeparatorChar	Returns the character placed between a volume letter and the rest of the path (typically, :, as in C:\Tests\Billing\ 2005q2.dat).

The following table summarizes the Path class’s most useful methods.

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Method	Purpose
ChangeExtension	Changes a path’s extension.
Combine	Returns two path strings concatenated. This does not simplify the result as the FileSystem.CombinePath method does.
GetDirectoryName	Returns a path’s directory.
GetExtension	Returns a path’s extension.
GetFileName	Returns a path’s file name and extension.
GetFileNameWithoutExtension	Returns a path’s file name without the extension.
GetFullPath	Returns a path’s fully qualified value. This can be particularly useful for converting a partially relative path into an absolute path. For example, the statement Path.GetFullPath(“C:\ Tests\OldTests\Software\..\..\New\Code”) returns C:\Tests\New\Code.
GetInvalidFileNameChars	Returns a character array that holds characters that are not allowed in a file names.
GetPathRoot	Returns a path’s root directory string. For example, the statement Path.GetPathRoot(“C:\Invoices\Unpaid\ Deadbeats”) returns C:\.
GetRandomFileName	Returns a random file name.
GetTempFileName	Creates a uniquely named, empty temporary file, and returns its fully qualified path. Your program can open that file for scratch space, do whatever it needs to do, close the file, and then delete it. A typical file name might be C:\Documents and Settings\Rod\Local Settings\Temp\tmp19D.tmp.
GetTempPath	Returns the path to the system’s temporary folder. This is the path part of the file name returned by GetTempFileName.
HasExtension	Returns True if a path includes an extension.
IsPathRooted	Returns True if a path is an absolute path. This includes \Temp\Wherever and C:\Clients\Litigation, but not Temp\Wherever or ..\Uncle.