FileSystemWatcher.Filter Property

 

Gets or sets the filter string used to determine what files are monitored in a directory.

Namespace:   System.IO
Assembly:  System (in System.dll)

<IODescriptionAttribute("FSW_Filter")>
<TypeConverterAttribute("System.Diagnostics.Design.StringValueConverter, System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")>
<SettingsBindableAttribute(True)>
Public Property Filter As String

Property Value

Type: System.String

The filter string. The default is "*.*" (Watches all files.)

To watch changes in all files, set the Filter property to an empty string (""). To watch a specific file, set the Filter property to the file name. For example, to watch for changes in the file MyDoc.txt, set the Filter property to "MyDoc.txt". You can also watch for changes in a certain type of file. For example, to watch for changes in any text files, set the Filter property to "*.txt". Use of multiple filters such as "*.txt|*.doc" is not supported.

The Filter property can be changed after the FileSystemWatcher object has started receiving events.

For more information about filtering out unwanted notifications, see the NotifyFilter, IncludeSubdirectories, and InternalBufferSize properties.

Filter accepts wildcards for matching files, as shown in the following examples.

Filter string

Watches the following files

*.*

All files (default). An empty string ("") also watches all files.

*.txt

All files with a "txt" extension.

*recipe.doc

All files ending in "recipe" with a "doc" extension.

win*.xml

All files beginning with "win" with an "xml" extension.

Sales*200?.xls

Matches the following:

Sales July 2001.xlsSales Aug 2002.xlsSales March 2004.xls

but does not match:

Sales Nov 1999.xls

MyReport.Doc

Watches only MyReport.doc

The following example creates a FileSystemWatcher to watch the directory specified at run time. The component is set to watch for changes in LastWrite and LastAccess time, the creation, deletion, or renaming of text files in the directory. If a file is changed, created, or deleted, the path to the file prints to the console. When a file is renamed, the old and new paths print to the console.

Use the System.Diagnostics and System.IO namespaces for this example.

Imports System
Imports System.IO
Imports Microsoft.VisualBasic
Imports System.Security.Permissions

Public Class Watcher

    Public Shared Sub Main()

         Run()

    End Sub

    <PermissionSet(SecurityAction.Demand, Name:="FullTrust")> _
    Private Shared Sub Run

      Dim args() As String = System.Environment.GetCommandLineArgs()
        ' If a directory is not specified, exit the program.
        If args.Length <> 2 Then
            ' Display the proper way to call the program.
            Console.WriteLine("Usage: Watcher.exe (directory)")
            Return
        End If

        ' Create a new FileSystemWatcher and set its properties.
        Dim watcher As New FileSystemWatcher()
        watcher.Path = args(1)
        ' Watch for changes in LastAccess and LastWrite times, and
        ' the renaming of files or directories. 
        watcher.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.FileName Or NotifyFilters.DirectoryName)
        ' Only watch text files.
        watcher.Filter = "*.txt"

        ' Add event handlers.
        AddHandler watcher.Changed, AddressOf OnChanged
        AddHandler watcher.Created, AddressOf OnChanged
        AddHandler watcher.Deleted, AddressOf OnChanged
        AddHandler watcher.Renamed, AddressOf OnRenamed

        ' Begin watching.
        watcher.EnableRaisingEvents = True

        ' Wait for the user to quit the program.
        Console.WriteLine("Press 'q' to quit the sample.")
        While Chr(Console.Read()) <> "q"c
        End While
    End Sub

    ' Define the event handlers.
    Private Shared Sub OnChanged(source As Object, e As FileSystemEventArgs)
        ' Specify what is done when a file is changed, created, or deleted.
        Console.WriteLine("File: " & e.FullPath & " " & e.ChangeType)
    End Sub    

    Private Shared Sub OnRenamed(source As Object, e As RenamedEventArgs)
        ' Specify what is done when a file is renamed.
        Console.WriteLine("File: {0} renamed to {1}", e.OldFullPath, e.FullPath)
    End Sub

End Class

.NET Framework
Available since 1.1
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