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File.SetLastWriteTime Method

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

[Visual Basic]
Public Shared Sub SetLastWriteTime( _
   ByVal path As String, _
   ByVal lastWriteTime As DateTime _
)
[C#]
public static void SetLastWriteTime(
 string path,
 DateTime lastWriteTime
);
[C++]
public: static void SetLastWriteTime(
 String* path,
 DateTime lastWriteTime
);
[JScript]
public static function SetLastWriteTime(
   path : String,
 lastWriteTime : DateTime
);

Parameters

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

Exceptions

Exception Type Condition
ArgumentException path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.
ArgumentNullException path is a null reference (Nothing in Visual Basic).
PathTooLongException 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.
FileNotFoundException The specified path was not found.
UnauthorizedAccessException The caller does not have the required permission.
NotSupportedException path is in an invalid format.

Remarks

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 an example of using this method, see the Example section below. The following table lists examples of other typical or related I/O tasks.

To do this... See the example in this topic...
Write to a text file. Writing Text to a File
Read from a text file. Reading Text from a File
Append text to a file. Opening and Appending to a Log File

File.AppendText

FileInfo.AppendText

Rename or move a file. File.Move

FileInfo.MoveTo

Example

[Visual Basic, C#, C++] 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.

[Visual Basic] 
Imports System
Imports System.IO
Imports System.Text

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

            If File.Exists(path) = False Then
                File.Create(path)
            Else
                ' 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

[C#] 
using System;
using System.IO;

class Test 
{
    public static void Main() 
    {
        try 
        {
            string path = @"c:\Temp\MyTest.txt";
            if (!File.Exists(path)) 
            {
                File.Create(path);
            } 
            else 
            {
                // Take an action that will affect the write time.
                File.SetLastWriteTime(path, new DateTime(1985,4,3));
            }

            // Get the creation time of a well-known directory.
            DateTime dt = 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 (Exception e) 
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    }
}

[C++] 
#using <mscorlib.dll>

using namespace System;
using namespace System::IO;

int main() {
    try {
        String* path = S"c:\\Temp\\MyTest.txt";
        if (!File::Exists(path)) {
            File::Create(path);
        } else {
            // Take an action that will affect the write time.
            File::SetLastWriteTime(path, DateTime(1985,4,3));
        }

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

        // Update the last write time.
        File::SetLastWriteTime(path, DateTime::Now);
        dt = File::GetLastWriteTime(path);
        Console::WriteLine(S"The last write time for this file was {0}.", __box(dt));
    } catch (Exception* e) {
        Console::WriteLine(S"The process failed: {0}", e);
    }
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, Common Language Infrastructure (CLI) Standard

.NET Framework Security: 

See Also

File Class | File Members | System.IO Namespace | Working with I/O | Reading Text from a File | Writing Text to a File

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