Tuesday, February 12, 2008

FileSystemWatcher: Monitor for File changes using C#.Net

This example will show messages if there is any file change in the specified folder. But i added a file filter condition for text files(*.txt). So it will monintor only for txt files. The changes like create new file, rename a file, accessing files etc.. will be notified by a message Box.

The following code snippet will create a file watcher and initialize its properties, then enable it for monitoring.

FileSystemWatcher watcher = new FileSystemWatcher(); // Declares the FileSystemWatcher objectwatcher.Path = @"D:\MyDownloads"; // We have to specify the path which has to monitor
watcher.NotifyFilter = NotifyFilters.LastAccess NotifyFilters.LastWrite NotifyFilters.FileName notifyFilters.DirectoryName; // This property specifies which are the events to be monitoredwatcher.Filter = "*.txt"; // Only watch text files.// Add event handlers.
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.Created += new FileSystemEventHandler(OnChanged);
watcher.Deleted += new FileSystemEventHandler(OnChanged);
watcher.Renamed += new RenamedEventHandler(OnRenamed);
// Begin watching.
watcher.EnableRaisingEvents = true;

The following code for event handlers:

// Define the event handlers.
private static void OnChanged(object source, FileSystemEventArgs e)
// Specify what is done when a file is changed, created, or deleted.
MessageBox.Show("File: " + e.FullPath + " " + e.ChangeType);
private static void OnRenamed(object source, RenamedEventArgs e)
// Specify what is done when a file is renamed.
MessageBox.Show("File: "+ e.OldFullPath+" renamed to "+ e.FullPath);

Path class - VB.Net, C#.Net

The Path class provides methods for manipulating a file system path.
Path Methods

ChangeExtension: 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.)
Combine: Combines two compatible path strings.
GetDirectoryName: Returns the name of the directory in the specified path.
GetExtension: Returns the name of the file extension in the specified path.
GetFileName: Returns the name of the file in the specified path.
GetFileNameWithoutExtension: Returns the file name without the extension in the
specified path.
GetFullPath: Returns a full path to the specified path. This method can be used to resolve relative paths.
GetPathRoot: Returns the root directory name in the specified path.
GetRandomFileName: Generates a random file name.
GetTempFileName: Generates a temporary file in the file system and returns the full path to the file.
GetTempPath: Returns the path to the temporary file directory for the current user or system.
HasExtension: Indicates whether a specified path's file name has an extension.
IsPathRooted: Indicates whether the specified path includes a root directory.

DriveInfo - Listing Drives in C#.Net

DriveInfo[] mydrives = DriveInfo.GetDrives();

foreach (DriveInfo mydrive in mydrives)
Console.WriteLine("Drive: {0}", mydrive.Name);
Console.WriteLine("Type: {0}", mydrive.DriveType);

- GetDrives() is a static( shared in VB.Net) method.

- DriveType enumeration has the following values:
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 - A RAM drive.
Removable - A drive that has removable media.
Unknown - The drive could not be determined

DirectoryInfo class: Listing files in the specified directory - VB.Net, C#.Net

The DirectoryInfo class provides the basic functionality to access and manipulate a single directory in the file system.


Example: This exaple will list all files in the specified directory

DirectoryInfo myDir = new DirectoryInfo(@"H:\movies");

Console.WriteLine("Directory: {0}", myDir.FullName);

foreach (FileInfo myfile in myDir.GetFiles())
Console.WriteLine("File: {0}", myfile.Name);

How to copy, move files in C# .Net

Use system.IO namespace

FileInfo myfile = new FileInfo(@"H:\myphoto.jpg");

if (myfile.Exists)
myfile.CopyTo(@"H:\myphoto.bak",true );

- If the second parameter is true, the existing file will be replaced.
- If we specify an invalid path in MoveTo() it will throw DirectoryNotFoundException.

How to Get Information about File in c#.Net


FileInfo myfile = new FileInfo(@"H:\myphoto.jpg");

if (myfile.Exists)
Console.WriteLine("File name : {0}", myfile.Name);
Console.WriteLine("Path : {0}", myfile.FullName);
Console.WriteLine("Creation Time: {0}", myfile.CreationTime);
Console.WriteLine("Length : {0}", myfile.Length);

Note: "@" this symbol is used in string type to turn off escape processing. i.e If escape processing is turned on compiler will look for valid escape characters, if there is any invalid escape symbol it will throw compilation error.
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