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.NET Framework Class Library
FileSystemInfo..::.LastWriteTime Property

Updated: May 2010

Gets or sets the time when the current file or directory was last written to.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)
Visual Basic
Public Property LastWriteTime As DateTime
C#
public DateTime LastWriteTime { get; set; }
Visual C++
public:
property DateTime LastWriteTime {
    DateTime get ();
    void set (DateTime value);
}
F#
member LastWriteTime : DateTime with get, set

Property Value

Type: System..::.DateTime
The time the current file was last written.
ExceptionCondition
IOException

Refresh cannot initialize the data.

PlatformNotSupportedException

The current operating system is not Windows NT or later.

ArgumentOutOfRangeException

The caller attempts to set an invalid write time.

Note   This method may return an inaccurate value, because it uses native functions whose values may not be continuously updated by the operating system.

The value of the LastWriteTime property is pre-cached if the current instance of the FileSystemInfo object was returned from any of the following DirectoryInfo methods:

To get the latest value, call the Refresh method.

If the file described in the FileSystemInfo object does not exist, this property will return 12:00 midnight, January 1, 1601 A.D. (C.E.) Coordinated Universal Time (UTC), adjusted to local time.

This property value is nullNothingnullptra null reference (Nothing in Visual Basic) if the file system containing the file does not support this information.

Windows 95, Windows 98, Windows 98 Second Edition Platform Note: These operating systems do not support this property, and DirectoryInfo implementations of this property are not supported.

The following code example demonstrates the updating of the LastWriteTime property through a "touch" operation. In this example, the file is "touched", updating the CreationTime, LastAccessTime and LastWriteTime properties to the current date and time.

Visual Basic
Imports System
Imports System.IO

Public Class Touch
    Public Shared Sub Main(ByVal args() As String)

        ' Make sure an argument (filename) was provided.
        If args.Length > 0 Then

            ' Verify that the provided filename exists.
            If File.Exists(args(0)) Then
                Dim fi As FileInfo = New FileInfo(args(0))
                touchFile(fi)
            Else
                Console.WriteLine("Could not find the file {0}", args(0))
            End If
        Else
            Console.WriteLine("No file specified.")
        End If
    End Sub

    Public Shared Sub touchFile(ByVal fsi As FileSystemInfo)
        Console.WriteLine("Touching: {0}", fsi.FullName)

        ' Update the CreationTime, LastWriteTime and LastAccessTime.
        Try
            fsi.CreationTime = DateTime.Now
            fsi.LastAccessTime = DateTime.Now
            fsi.LastWriteTime = DateTime.Now
        Catch e As Exception
            Console.WriteLine("Error: {0}", e.Message)
        End Try

    End Sub

End Class
C#
using System;
using System.IO;

namespace touch
{
    class Touch
    {
        static void Main(string[] args)
        {
            // Make sure a filename was provided.
            if (args.Length > 0)
            {
                // Verify that the provided filename exists.
                if (File.Exists(args[0]))
                {
                    FileInfo fi = new FileInfo(args[0]);
                    touchFile(fi);
                }
                else
                {
                    Console.WriteLine(
                        "Could not find the file: {0}.", args[0]);
                }
            }
            else
            {
                Console.WriteLine("No file was specified.");
            }
        }

        static void touchFile(FileSystemInfo fsi)
        {
            Console.WriteLine("Touching: {0}", fsi.FullName);

            // Update the CreationTime, LastWriteTime and LastAccessTime.
            try
            {
                fsi.CreationTime = fsi.LastWriteTime = fsi.LastAccessTime =
                    DateTime.Now;
            }
            catch (Exception e)
            {
                Console.WriteLine("Error: {0}", e.Message);
            }
        }
    }
}

.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

Date

History

Reason

May 2010

Updated remarks.

Information enhancement.

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