DateTimeOffset.FromFileTime(Int64) Method
Definition
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.
Converts the specified Windows file time to an equivalent local time.
public:
static DateTimeOffset FromFileTime(long fileTime);public static DateTimeOffset FromFileTime (long fileTime);static member FromFileTime : int64 -> DateTimeOffsetPublic Shared Function FromFileTime (fileTime As Long) As DateTimeOffsetParameters
- fileTime
- Int64
A Windows file time, expressed in ticks.
Returns
An object that represents the date and time of fileTime with the offset set to the local time offset.
Exceptions
fileTime is less than zero.
-or-
fileTime is greater than DateTimeOffset.MaxValue.Ticks.
Examples
The following example uses the Windows API to retrieve the Windows file times for the WordPad executable.
using System;
using System.IO;
using System.Runtime.InteropServices;
public struct FileTime
{
public uint dwLowDateTime;
public uint dwHighDateTime;
public static implicit operator long(FileTime fileTime)
{
long returnedLong;
// Convert 4 high-order bytes to a byte array
byte[] highBytes = BitConverter.GetBytes(fileTime.dwHighDateTime);
// Resize the array to 8 bytes (for a Long)
Array.Resize(ref highBytes, 8);
// Assign high-order bytes to first 4 bytes of Long
returnedLong = BitConverter.ToInt64(highBytes, 0);
// Shift high-order bytes into position
returnedLong = returnedLong << 32;
// Or with low-order bytes
returnedLong = returnedLong | fileTime.dwLowDateTime;
// Return long
return returnedLong;
}
}
public class FileTimes
{
private const int OPEN_EXISTING = 3;
private const int INVALID_HANDLE_VALUE = -1;
[DllImport("Kernel32.dll", CharSet = CharSet.Unicode)]
private static extern int CreateFile(string lpFileName,
int dwDesiredAccess,
int dwShareMode,
int lpSecurityAttributes,
int dwCreationDisposition,
int dwFlagsAndAttributes,
int hTemplateFile);
[DllImport("Kernel32.dll")]
private static extern bool GetFileTime(int hFile,
out FileTime lpCreationTime,
out FileTime lpLastAccessTime,
out FileTime lpLastWriteTime);
[DllImport("Kernel32.dll")]
private static extern bool CloseHandle(int hFile);
public static void Main()
{
// Open file %windir%\write.exe
string winDir = Environment.SystemDirectory;
if (! (winDir.EndsWith(Path.DirectorySeparatorChar.ToString())))
winDir += Path.DirectorySeparatorChar;
winDir += "write.exe";
// Get file time using Windows API
//
// Open file
int hFile = CreateFile(winDir, 0, 0, 0, OPEN_EXISTING, 0, 0);
if (hFile == INVALID_HANDLE_VALUE)
{
Console.WriteLine("Unable to access {0}.", winDir);
}
else
{
FileTime creationTime, accessTime, writeTime;
if (GetFileTime(hFile, out creationTime, out accessTime, out writeTime))
{
CloseHandle(hFile);
long fileCreationTime = (long) creationTime;
long fileAccessTime = accessTime;
long fileWriteTime = (long) writeTime;
Console.WriteLine("File {0} Retrieved Using the Windows API:", winDir);
Console.WriteLine(" Created: {0:d}", DateTimeOffset.FromFileTime(fileCreationTime).ToString());
Console.WriteLine(" Last Access: {0:d}", DateTimeOffset.FromFileTime(fileAccessTime).ToString());
Console.WriteLine(" Last Write: {0:d}", DateTimeOffset.FromFileTime(fileWriteTime).ToString());
Console.WriteLine();
}
}
// Get date and time, convert to file time, then convert back
FileInfo fileInfo = new FileInfo(winDir);
DateTimeOffset infoCreationTime, infoAccessTime, infoWriteTime;
long ftCreationTime, ftAccessTime, ftWriteTime;
// Get dates and times of file creation, last access, and last write
infoCreationTime = fileInfo.CreationTime;
infoAccessTime = fileInfo.LastAccessTime;
infoWriteTime = fileInfo.LastWriteTime;
// Convert values to file times
ftCreationTime = infoCreationTime.ToFileTime();
ftAccessTime = infoAccessTime.ToFileTime();
ftWriteTime = infoWriteTime.ToFileTime();
// Convert file times back to DateTimeOffset values
Console.WriteLine("File {0} Retrieved Using a FileInfo Object:", winDir);
Console.WriteLine(" Created: {0:d}", DateTimeOffset.FromFileTime(ftCreationTime).ToString());
Console.WriteLine(" Last Access: {0:d}", DateTimeOffset.FromFileTime(ftAccessTime).ToString());
Console.WriteLine(" Last Write: {0:d}", DateTimeOffset.FromFileTime(ftWriteTime).ToString());
}
}
// The example produces the following output:
// File C:\WINDOWS\system32\write.exe Retrieved Using the Windows API:
// Created: 10/13/2005 5:26:59 PM -07:00
// Last Access: 3/20/2007 2:07:00 AM -07:00
// Last Write: 8/4/2004 5:00:00 AM -07:00
//
// File C:\WINDOWS\system32\write.exe Retrieved Using a FileInfo Object:
// Created: 10/13/2005 5:26:59 PM -07:00
// Last Access: 3/20/2007 2:07:00 AM -07:00
// Last Write: 8/4/2004 5:00:00 AM -07:00
open System
open System.IO
open System.Runtime.InteropServices
open FSharp.NativeInterop
[<Struct>]
type FileTime =
val dwLowDateTime: uint
val dwHighDateTime: uint
static member ToLong(fileTime: FileTime) =
// Convert 4 high-order bytes to a byte array
let mutable highBytes = BitConverter.GetBytes fileTime.dwHighDateTime
// Resize the array to 8 bytes (for a Long)
Array.Resize(&highBytes, 8)
// Assign high-order bytes to first 4 bytes of Long
let returnedLong = BitConverter.ToInt64(highBytes, 0)
// Shift high-order bytes into position
let returnedLong = returnedLong <<< 32
// Or with low-order bytes
returnedLong ||| int64 fileTime.dwLowDateTime
let [<Literal>] OPEN_EXISTING = 3
let [<Literal>] INVALID_HANDLE_VALUE = -1
[<DllImport("Kernel32.dll", CharSet = CharSet.Unicode)>]
extern int CreateFile(string lpFileName,
int dwDesiredAccess,
int dwShareMode,
int lpSecurityAttributes,
int dwCreationDisposition,
int dwFlagsAndAttributes,
int hTemplateFile)
[<DllImport "Kernel32.dll">]
extern bool GetFileTime(int hFile,
nativeint lpCreationTime,
nativeint lpLastAccessTime,
nativeint lpLastWriteTime)
[<DllImport "Kernel32.dll">]
extern bool CloseHandle(int hFile)
// Open file %windir%\write.exe
let winDir =
let winDir = Environment.SystemDirectory
let winDir =
if winDir.EndsWith(string Path.DirectorySeparatorChar) then
winDir
else
winDir + string Path.DirectorySeparatorChar
winDir + "write.exe"
// Get file time using Windows API
// Open file
let hFile = CreateFile(winDir, 0, 0, 0, OPEN_EXISTING, 0, 0)
if hFile = INVALID_HANDLE_VALUE then
printfn $"Unable to access {winDir}."
else
let mutable creationTime = Unchecked.defaultof<FileTime>
let mutable accessTime = Unchecked.defaultof<FileTime>
let mutable writeTime = Unchecked.defaultof<FileTime>
if GetFileTime(hFile, NativePtr.toNativeInt &&creationTime, NativePtr.toNativeInt &&accessTime, NativePtr.toNativeInt &&writeTime) then
let fileCreationTime = FileTime.ToLong creationTime
let fileAccessTime = FileTime.ToLong accessTime
let fileWriteTime = FileTime.ToLong writeTime
printfn $"File {winDir} Retrieved Using the Windows API:"
printfn $" Created: {DateTimeOffset.FromFileTime fileCreationTime |> string:d}"
printfn $" Last Access: {DateTimeOffset.FromFileTime fileAccessTime |> string:d}"
printfn $" Last Write: {DateTimeOffset.FromFileTime fileWriteTime |> string:d}\n"
// Get date and time, convert to file time, then convert back
let fileInfo = FileInfo winDir
// Get dates and times of file creation, last access, and last write
let infoCreationTime = fileInfo.CreationTime
let infoAccessTime = fileInfo.LastAccessTime
let infoWriteTime = fileInfo.LastWriteTime
// Convert values to file times
let ftCreationTime = infoCreationTime.ToFileTime()
let ftAccessTime = infoAccessTime.ToFileTime()
let ftWriteTime = infoWriteTime.ToFileTime()
// Convert file times back to DateTimeOffset values
printfn $"File {winDir} Retrieved Using a FileInfo Object:"
printfn $" Created: {DateTimeOffset.FromFileTime ftCreationTime |> string:d}"
printfn $" Last Access: {DateTimeOffset.FromFileTime ftAccessTime |> string:d}"
printfn $" Last Write: {DateTimeOffset.FromFileTime ftWriteTime |> string:d}"
// The example produces the following output:
// File C:\WINDOWS\system32\write.exe Retrieved Using the Windows API:
// Created: 10/13/2005 5:26:59 PM -07:00
// Last Access: 3/20/2007 2:07:00 AM -07:00
// Last Write: 8/4/2004 5:00:00 AM -07:00
//
// File C:\WINDOWS\system32\write.exe Retrieved Using a FileInfo Object:
// Created: 10/13/2005 5:26:59 PM -07:00
// Last Access: 3/20/2007 2:07:00 AM -07:00
// Last Write: 8/4/2004 5:00:00 AM -07:00
Imports System.IO
Public Structure FileTime
Public dwLowDateTime As UInteger
Public dwHighDateTime As UInteger
Public Shared Widening Operator CType(fileTime As FileTime) As Long
Dim returnedLong As Long
' Convert 4 high-order bytes to a byte array
Dim highBytes() As Byte = BitConverter.GetBytes(fileTime.dwHighDateTime)
' Resize the array to 8 bytes (for a Long)
ReDim Preserve highBytes(7)
' Assign high-order bytes to first 4 bytes of Long
returnedLong = BitConverter.ToInt64(highBytes, 0)
' Shift high-order bytes into position
returnedLong = returnedLong << 32
' Or with low-order bytes
returnedLong = returnedLong Or fileTime.dwLowDateTime
' Return Long
return returnedLong
End Operator
End Structure
Module modMain
Private Const OPEN_EXISTING As Integer = 3
Private Const INVALID_HANDLE_VALUE As Integer = -1
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" ( _
ByVal lpFileName As String, _
ByVal dwDesiredAccess As Integer, _
ByVal dwShareMode As Integer, _
ByVal lpSecurityAttributes As Integer, _
ByVal dwCreationDisposition As Integer, _
ByVal dwFlagsAndAttributes As Integer, _
ByVal hTemplateFile As Integer) _
As Integer
Private Declare Function GetFileTime Lib "Kernel32"( _
hFile As Integer, _
ByRef lpCreationTime As FileTime, _
ByRef lpLastAccessTime As FileTime, _
ByRef lpLastWriteTime As FileTime) _
As Boolean
Private Declare Function CloseHandle Lib "Kernel32" ( _
hFile As Integer) _
As Boolean
Public Sub Main()
' Open file %windir%\write.exe
Dim winDir As String = Environment.SystemDirectory
If Not winDir.EndsWith(Path.DirectorySeparatorChar) Then _
winDir += Path.DirectorySeparatorChar
windir += "write.exe"
' Get file time using Windows API
'
' Open file
Dim hFile As Integer = CreateFile(winDir, 0, 0, 0, _
OPEN_EXISTING, 0, 0)
If hFile = INVALID_HANDLE_VALUE Then
Console.WriteLine("Unable to access {0}.", winDir)
Else
Dim creationTime, accessTime, writeTime As FileTime
If GetFileTime(hFile, creationTime, accessTime, writeTime) Then
CloseHandle(hFile)
Dim fileCreationTime As Long = CType(creationTime, Long)
Dim fileAccessTime As Long = CType(accessTime, Long)
Dim fileWriteTime As Long = CType(writeTime, Long)
Console.WriteLine("File {0} Retrieved Using the Windows API:", winDir)
Console.WriteLine(" Created: {0:d}", DateTimeOffset.FromFileTime(fileCreationTime).ToString())
Console.WriteLine(" Last Access: {0:d}", DateTimeOffset.FromFileTime(fileAccessTime).ToString())
Console.WriteLine(" Last Write: {0:d}", DateTimeOffset.FromFileTime(fileWriteTime).ToString())
Console.WriteLine()
End If
End If
' Get date and time, convert to file time, then convert back
Dim fileInfo As New FileInfo(winDir)
Dim infoCreationTime, infoAccessTime, infoWriteTime As DateTimeOffset
Dim ftCreationTime, ftAccessTime, ftWriteTime As Long
' Get dates and times of file creation, last access, and last write
infoCreationTime = fileInfo.CreationTime
infoAccessTime = fileInfo.LastAccessTime
infoWriteTime = fileInfo.LastWriteTime
' Convert values to file times
ftCreationTime = infoCreationTime.ToFileTime()
ftAccessTime = infoAccessTime.ToFileTime()
ftWriteTime = infoWriteTime.ToFileTime()
' Convert file times back to DateTimeOffset values
Console.WriteLine("File {0} Retrieved Using a FileInfo Object:", winDir)
Console.WriteLine(" Created: {0:d}", DateTimeOffset.FromFileTime(ftCreationTime).ToString())
Console.WriteLine(" Last Access: {0:d}", DateTimeOffset.FromFileTime(ftAccessTime).ToString())
Console.WriteLine(" Last Write: {0:d}", DateTimeOffset.FromFileTime(ftWriteTime).ToString())
End Sub
End Module
' The example produces the following output:
' File C:\WINDOWS\system32\write.exe Retrieved Using the Windows API:
' Created: 10/13/2005 5:26:59 PM -07:00
' Last Access: 3/20/2007 2:07:00 AM -07:00
' Last Write: 8/4/2004 5:00:00 AM -07:00
'
' File C:\WINDOWS\system32\write.exe Retrieved Using a FileInfo Object:
' Created: 10/13/2005 5:26:59 PM -07:00
' Last Access: 3/20/2007 2:07:00 AM -07:00
' Last Write: 8/4/2004 5:00:00 AM -07:00
Remarks
A Windows file time is a 64-bit value that represents the number of 100-nanosecond intervals that have elapsed since 12:00 midnight, January 1, 1601 A.D. (C.E.) Coordinated Universal Time (UTC). Windows uses a file time to record when an application creates, accesses, or writes to a file.
A Windows file time is directly accessible through the Windows API by calling the GetFileTime function, which returns a FILETIME structure. The single function parameter is the handle of the file whose file time information is to be retrieved. The file handle is retrieved by calling the CreateFile function. The FILETIME structure's dwHighDateTime member contains the four high-order bytes of the file time, and its dwLowDateTime member contains the four low-order bytes. The example that follows illustrates how to retrieve Windows file time values and convert them to DateTimeOffset values.
Windows file time values can also be created from DateTime values by calling the DateTime.ToFileTime and DateTime.ToFileTimeUtc methods, and from DateTimeOffset values by calling the DateTimeOffset.ToFileTime method.
Applies to
Samarbeta med oss på GitHub
Källan för det här innehållet finns på GitHub, där du även kan skapa och granska ärenden och pull-begäranden. Se vår deltagarguide för mer information.
