File.SetLastWriteTime Method (String, DateTime)


Sets the date and time that the specified file was last written to.

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

Public Shared Sub SetLastWriteTime (
	path As String,
	lastWriteTime As Date


Type: System.String

The file for which to set the date and time information.

Type: System.DateTime

A DateTime containing the value to set for the last write date and time of path. This value is expressed in local time.

Exception Condition

path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.


path is null.


The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.


The specified path was not found.


The caller does not have the required permission.


path is in an invalid format.


lastWriteTime specifies a value outside the range of dates or times permitted for this operation.

The path parameter is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see GetCurrentDirectory.

For a list of common I/O tasks, see Common I-O Tasks.

The following example checks the file system for the specified file, creating the file if necessary, and then sets and gets the last write time of the file.

Imports System
Imports System.IO
Imports System.Text

Public Class Test
    Public Shared Sub Main()
            Dim path As String = "c:\Temp\MyTest.txt"

            If File.Exists(path) = False Then
                ' Take an action that will affect the write time.
                File.SetLastWriteTime(path, New DateTime(1985, 4, 3))
            End If

            ' Get the creation time of a well-known directory.
            Dim dt As DateTime = File.GetLastWriteTime(path)
            Console.WriteLine("The last write time for this file was {0}.", dt)

            ' Update the last write time.
            File.SetLastWriteTime(path, DateTime.Now)
            dt = File.GetLastWriteTime(path)
            Console.WriteLine("The last write time for this file was {0}.", dt)

        Catch e As Exception
            Console.WriteLine("The process failed: {0}", e.ToString())
        End Try
    End Sub
End Class


for writing to the specified file. Associated enumeration: FileIOPermissionAccess.Write

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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