http://technet.microsoft.com/zh-cn/magazine/system.io.file.getlastwritetime(de-de).aspx

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 some 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