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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")]
[SettingsBindableAttribute(true)]
[TypeConverterAttribute("System.Diagnostics.Design.StringValueConverter, System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
public string Filter { get; set; }

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.

using System;
using System.IO;
using System.Security.Permissions;

public class Watcher
{

    public static void Main()
    {
    Run();

    }

    [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
    public static void Run()
    {
        string[] args = System.Environment.GetCommandLineArgs();

        // If a directory is not specified, exit program. 
        if(args.Length != 2)
        {
            // Display the proper way to call the program.
            Console.WriteLine("Usage: Watcher.exe (directory)");
            return;
        }

        // Create a new FileSystemWatcher and set its properties.
        FileSystemWatcher watcher = 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 | NotifyFilters.LastWrite
           | NotifyFilters.FileName | NotifyFilters.DirectoryName;
        // Only watch text files.
        watcher.Filter = "*.txt";

        // 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;

        // Wait for the user to quit the program.
        Console.WriteLine("Press \'q\' to quit the sample.");
        while(Console.Read()!='q');
    }

    // Define the event handlers. 
    private static void OnChanged(object source, FileSystemEventArgs e)
    {
        // Specify what is done when a file is changed, created, or deleted.
       Console.WriteLine("File: " +  e.FullPath + " " + e.ChangeType);
    }

    private static void OnRenamed(object source, RenamedEventArgs e)
    {
        // Specify what is done when a file is renamed.
        Console.WriteLine("File: {0} renamed to {1}", e.OldFullPath, e.FullPath);
    }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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