Monitoring a Folder using FileSystemWatcher class in .NetFileSystemWatcher class provided in .Net is used for monitoring the activities in a folder or sub-folders. You can watch the folder for specific types of files or all the types of files. You can watch for changes like creating a file, deleting a file, changing a file content etc. although you can create such applications in VB6, it is a tedious task since you have to write a lot of code for achieving that task. But in .Net this task can be done very easily by using the class called the FileSystemWatcher class.
The namespaces
that you have to import for using this class are System.IO and System.Diagnostics.
To monitor a folder for any activities all you have to do is to create
an instance of the FileSystemWatcher class and set the necessary properties
and invoke methods. You have to create handlers for the FileSystem events.
With all of these done you are ready to watch the activities on a particular
folder in your system. You can also watch for activities on remote folders
using this FileSystemWatcher class. Creating
an instance of FileSystemWatcher class is just like creating an instance
for other classes. The code for creating an instance would look like, FileSystemWatcher
myFolderWatcher = new FileSystemWatcher(); The properties
for the FileSystemWatcher class that needs to be set are the Path and
the Filter property. The path property sets the path of the folder that
is to be watched. The filter property sets the filter for the types of
files to be watched. For example if you want to watch for the activities
of the word documents in a folder, you can set the filter property to
“*.doc”. It is possible
to pass the properties and the filters even while you create an instance
of the FileSystemWatcher class. If you are passing these properties while
you create an instance, the code will look like, FileSystemWatcher
myFolderWatcher = new FileSystemWatcher(“d:\\”, “*.doc”); The properties
that are usually used in this class are the Path, EnableRaisingEvents,
Filter, IncludeSubdirectories, InternalBufferSize, and NotifyFilter. Setting
the IncludeSubdirectories enables you to watch for changes in the subdirectories
of the path set. The NotifyFilter property gets or sets the type of changes
to look for in the folders/subfolders. The NotifyFilter
property can be set to any of the NotifyFilters enumeration values. The
enumeration values that are of interest are, Attributes, CreationTime,
DirectoryName, FileName, LastAccess, LastWrite, Security, and Size. The events
for which we usually write code are the Changed, Created, Deleted, Error,
and Renamed. The Changed event is raised when a file or directory in the
path specified changes. The Created event occurs when file is created.
The Deleted event is raised when a file or directory is deleted. The Error
event is raised when there is an internal buffer overflow. The Renamed
event is raised when a file or directory is renamed. Some of the
protected methods for the FileSystemWatcher class are OnChanged, OnCreated,
OnDeleted, OnError, and OnRenamed. There is no need for explanation on
what these methods do. The name itself indicates that. A simple
example of a code snippet that is used to track changes to the documents
in a folder is given below. Imports System.IO myFolderWatcher.Path
= "......give path to the folder here...." myFolderWatcher.NotifyFilter
= IO.NotifyFilters.DirectoryName AddHandler
myFolderWatcher.Changed, AddressOf ActivityMesg myFolderWatcher.EnableRaisingEvents
= True In the above
code we have first imported the namespaces required and then created an
object of FileSystemWatcher class. We have set the path of the folder
to be watched for. Set the NotifyFilter property to one of the enumeration
values of the enumerator NotifyFilters. Set the FileSystemWatcher object’s
EnableRaisingEvents to True to start tracking the events. Add a handler
for the Changed event. With this the application would start tracking
the changes in the folder mentioned. You can add other events also in
the same program and use other NotifyFilters enumeration values to make
the program fully functional. Thus we find
that the FileSystemWatcher class is very easy to use to track the activities
of a particular folder in your computer or network.
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