FileSystemWatcher Constructors

Reference

Definition

Namespace:: System.IO

Assemblies:: netstandard.dll, System.IO.FileSystem.Watcher.dll

Assembly:: System.IO.FileSystem.Watcher.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Initializes a new instance of the FileSystemWatcher class.

Overloads

FileSystemWatcher()	Initializes a new instance of the FileSystemWatcher class.
FileSystemWatcher(String)	Initializes a new instance of the FileSystemWatcher class, given the specified directory to monitor.
FileSystemWatcher(String, String)	Initializes a new instance of the FileSystemWatcher class, given the specified directory and type of files to monitor.

FileSystemWatcher()

Source:: FileSystemWatcher.cs

Source:: FileSystemWatcher.cs

Source:: FileSystemWatcher.cs

Initializes a new instance of the FileSystemWatcher class.

public:
 FileSystemWatcher();

public FileSystemWatcher();

Public Sub New ()

Examples

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

This example uses the System.Diagnostics and System.IO namespaces.

#include "pch.h"

using namespace System;
using namespace System::IO;

class MyClassCPP
{
public:

    int static Run()
    {
        FileSystemWatcher^ watcher = gcnew FileSystemWatcher("C:\\path\\to\\folder");

        watcher->NotifyFilter = static_cast<NotifyFilters>(NotifyFilters::Attributes
                                                         | NotifyFilters::CreationTime
                                                         | NotifyFilters::DirectoryName
                                                         | NotifyFilters::FileName
                                                         | NotifyFilters::LastAccess
                                                         | NotifyFilters::LastWrite
                                                         | NotifyFilters::Security
                                                         | NotifyFilters::Size);

        watcher->Changed += gcnew FileSystemEventHandler(MyClassCPP::OnChanged);
        watcher->Created += gcnew FileSystemEventHandler(MyClassCPP::OnCreated);
        watcher->Deleted += gcnew FileSystemEventHandler(MyClassCPP::OnDeleted);
        watcher->Renamed += gcnew RenamedEventHandler(MyClassCPP::OnRenamed);
        watcher->Error   += gcnew ErrorEventHandler(MyClassCPP::OnError);

        watcher->Filter = "*.txt";
        watcher->IncludeSubdirectories = true;
        watcher->EnableRaisingEvents = true;

        Console::WriteLine("Press enter to exit.");
        Console::ReadLine();

        return 0;
    }

private:

    static void OnChanged(Object^ sender, FileSystemEventArgs^ e)
    {
        if (e->ChangeType != WatcherChangeTypes::Changed)
        {
            return;
        }
        Console::WriteLine("Changed: {0}", e->FullPath);
    }

    static void OnCreated(Object^ sender, FileSystemEventArgs^ e)
    {
        Console::WriteLine("Created: {0}", e->FullPath);
    }

    static void OnDeleted(Object^ sender, FileSystemEventArgs^ e)
    {
        Console::WriteLine("Deleted: {0}", e->FullPath);
    }

    static void OnRenamed(Object^ sender, RenamedEventArgs^ e)
    {
        Console::WriteLine("Renamed:");
        Console::WriteLine("    Old: {0}", e->OldFullPath);
        Console::WriteLine("    New: {0}", e->FullPath);
    }

    static void OnError(Object^ sender, ErrorEventArgs^ e)
    {
        PrintException(e->GetException());
    }

    static void PrintException(Exception^ ex)
    {
        if (ex != nullptr)
        {
            Console::WriteLine("Message: {0}", ex->Message);
            Console::WriteLine("Stacktrace:");
            Console::WriteLine(ex->StackTrace);
            Console::WriteLine();
            PrintException(ex->InnerException);
        }
    }
};


int main()
{
    MyClassCPP::Run();
}

using System;
using System.IO;

namespace MyNamespace
{
    class MyClassCS
    {
        static void Main()
        {
            using var watcher = new FileSystemWatcher(@"C:\path\to\folder");

            watcher.NotifyFilter = NotifyFilters.Attributes
                                 | NotifyFilters.CreationTime
                                 | NotifyFilters.DirectoryName
                                 | NotifyFilters.FileName
                                 | NotifyFilters.LastAccess
                                 | NotifyFilters.LastWrite
                                 | NotifyFilters.Security
                                 | NotifyFilters.Size;

            watcher.Changed += OnChanged;
            watcher.Created += OnCreated;
            watcher.Deleted += OnDeleted;
            watcher.Renamed += OnRenamed;
            watcher.Error += OnError;

            watcher.Filter = "*.txt";
            watcher.IncludeSubdirectories = true;
            watcher.EnableRaisingEvents = true;

            Console.WriteLine("Press enter to exit.");
            Console.ReadLine();
        }

        private static void OnChanged(object sender, FileSystemEventArgs e)
        {
            if (e.ChangeType != WatcherChangeTypes.Changed)
            {
                return;
            }
            Console.WriteLine($"Changed: {e.FullPath}");
        }

        private static void OnCreated(object sender, FileSystemEventArgs e)
        {
            string value = $"Created: {e.FullPath}";
            Console.WriteLine(value);
        }

        private static void OnDeleted(object sender, FileSystemEventArgs e) =>
            Console.WriteLine($"Deleted: {e.FullPath}");

        private static void OnRenamed(object sender, RenamedEventArgs e)
        {
            Console.WriteLine($"Renamed:");
            Console.WriteLine($"    Old: {e.OldFullPath}");
            Console.WriteLine($"    New: {e.FullPath}");
        }

        private static void OnError(object sender, ErrorEventArgs e) =>
            PrintException(e.GetException());

        private static void PrintException(Exception? ex)
        {
            if (ex != null)
            {
                Console.WriteLine($"Message: {ex.Message}");
                Console.WriteLine("Stacktrace:");
                Console.WriteLine(ex.StackTrace);
                Console.WriteLine();
                PrintException(ex.InnerException);
            }
        }
    }
}

Imports System.IO

Namespace MyNamespace

    Class MyClassVB

        Shared Sub Main()
            Using watcher = New FileSystemWatcher("C:\path\to\folder")
                watcher.NotifyFilter = NotifyFilters.Attributes Or
                                       NotifyFilters.CreationTime Or
                                       NotifyFilters.DirectoryName Or
                                       NotifyFilters.FileName Or
                                       NotifyFilters.LastAccess Or
                                       NotifyFilters.LastWrite Or
                                       NotifyFilters.Security Or
                                       NotifyFilters.Size

                AddHandler watcher.Changed, AddressOf OnChanged
                AddHandler watcher.Created, AddressOf OnCreated
                AddHandler watcher.Deleted, AddressOf OnDeleted
                AddHandler watcher.Renamed, AddressOf OnRenamed
                AddHandler watcher.Error, AddressOf OnError

                watcher.Filter = "*.txt"
                watcher.IncludeSubdirectories = True
                watcher.EnableRaisingEvents = True

                Console.WriteLine("Press enter to exit.")
                Console.ReadLine()
            End Using
        End Sub

        Private Shared Sub OnChanged(sender As Object, e As FileSystemEventArgs)
            If e.ChangeType <> WatcherChangeTypes.Changed Then
                Return
            End If
            Console.WriteLine($"Changed: {e.FullPath}")
        End Sub

        Private Shared Sub OnCreated(sender As Object, e As FileSystemEventArgs)
            Dim value As String = $"Created: {e.FullPath}"
            Console.WriteLine(value)
        End Sub

        Private Shared Sub OnDeleted(sender As Object, e As FileSystemEventArgs)
            Console.WriteLine($"Deleted: {e.FullPath}")
        End Sub

        Private Shared Sub OnRenamed(sender As Object, e As RenamedEventArgs)
            Console.WriteLine($"Renamed:")
            Console.WriteLine($"    Old: {e.OldFullPath}")
            Console.WriteLine($"    New: {e.FullPath}")
        End Sub

        Private Shared Sub OnError(sender As Object, e As ErrorEventArgs)
            PrintException(e.GetException())
        End Sub

        Private Shared Sub PrintException(ex As Exception)
            If ex IsNot Nothing Then
                Console.WriteLine($"Message: {ex.Message}")
                Console.WriteLine("Stacktrace:")
                Console.WriteLine(ex.StackTrace)
                Console.WriteLine()
                PrintException(ex.InnerException)
            End If
        End Sub

    End Class

End Namespace

Remarks

You cannot watch a remote computer that does not have Windows NT or Windows 2000. You cannot watch a remote Windows NT 4.0 computer from a Windows NT 4.0 computer.

The following table shows initial property values for an instance of FileSystemWatcher.

Property	Initial Value
NotifyFilter	bitwise OR combination of `LastWrite`, `FileName`, and `DirectoryName`
EnableRaisingEvents	`false`
Filter	"." (Watch all files.)
IncludeSubdirectories	`false`
InternalBufferSize	8192
Path	empty string ("")

Note

The component will not watch the specified directory until the Path is set, and EnableRaisingEvents is true.

Applies to

.NET 10 and other versions

Product	Versions
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	2.0, 2.1

FileSystemWatcher(String)

Source:: FileSystemWatcher.cs

Source:: FileSystemWatcher.cs

Source:: FileSystemWatcher.cs

Initializes a new instance of the FileSystemWatcher class, given the specified directory to monitor.

public:
 FileSystemWatcher(System::String ^ path);

public FileSystemWatcher(string path);

new System.IO.FileSystemWatcher : string -> System.IO.FileSystemWatcher

Public Sub New (path As String)

Parameters

path: String

The directory to monitor, in standard or Universal Naming Convention (UNC) notation.

Exceptions

ArgumentNullException

The path parameter is null.

ArgumentException

The path parameter is an empty string ("").

-or-

The path specified through the path parameter does not exist.

PathTooLongException

path is too long.

Remarks

Note

The component will not watch the specified directory until the Path is set, and EnableRaisingEvents is true.

The component can watch files on your personal computer, a network drive, or a remote computer.

You cannot watch a remote computer that does not have Windows NT or Windows 2000. You cannot watch a remote Windows NT 4.0 computer from a Windows NT 4.0 computer. The Filter property is set by default to watch all files.

Applies to

.NET 10 and other versions

Product	Versions
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	2.0, 2.1

FileSystemWatcher(String, String)

Source:: FileSystemWatcher.cs

Source:: FileSystemWatcher.cs

Source:: FileSystemWatcher.cs

Initializes a new instance of the FileSystemWatcher class, given the specified directory and type of files to monitor.

public:
 FileSystemWatcher(System::String ^ path, System::String ^ filter);

public FileSystemWatcher(string path, string filter);

new System.IO.FileSystemWatcher : string * string -> System.IO.FileSystemWatcher

Public Sub New (path As String, filter As String)

Parameters

path: String

The directory to monitor, in standard or Universal Naming Convention (UNC) notation.

filter: String

The type of files to watch. For example, "*.txt" watches for changes to all text files.

Exceptions

ArgumentNullException

The path parameter is null.

-or-

The filter parameter is null.

ArgumentException

The path parameter is an empty string ("").

-or-

The path specified through the path parameter does not exist.

PathTooLongException

path is too long.

Remarks

Note

The component will not watch the specified directory until the Path is set, and EnableRaisingEvents is true.

The component can watch files on your personal computer, a network drive, or a remote computer.

You cannot watch a remote computer that does not have Windows NT or Windows 2000. You cannot watch a remote Windows NT 4.0 computer from a Windows NT 4.0 computer.

Applies to

.NET 10 and other versions

Product	Versions
.NET	Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	2.0, 2.1

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FileSystemWatcher Constructors

Definition

Overloads

FileSystemWatcher()

Examples

Remarks

See also

Applies to

FileSystemWatcher(String)

Parameters

Exceptions

Remarks

See also

Applies to

FileSystemWatcher(String, String)

Parameters

Exceptions

Remarks

See also

Applies to

Additional resources