DateTimeOffset.FromFileTime(Int64) Metoda
Definice
Důležité
Některé informace platí pro předběžně vydaný produkt, který se může zásadně změnit, než ho výrobce nebo autor vydá. Microsoft neposkytuje žádné záruky, výslovné ani předpokládané, týkající se zde uváděných informací.
Převede zadaný čas souboru Systému Windows na ekvivalentní místní čas.
public:
static DateTimeOffset FromFileTime(long fileTime);public static DateTimeOffset FromFileTime (long fileTime);static member FromFileTime : int64 -> DateTimeOffsetPublic Shared Function FromFileTime (fileTime As Long) As DateTimeOffsetParametry
- fileTime
- Int64
Čas souboru Systému Windows vyjádřený v ticks.
Návraty
Objekt, který představuje datum a čas fileTime s posunem nastaveným na místní časový posun.
Výjimky
fileTime je menší než nula.
-nebo-
fileTime je větší než DateTimeOffset.MaxValue.Ticks.
Příklady
Následující příklad používá rozhraní API systému Windows k načtení časů souborů systému Windows pro spustitelný soubor WordPad.
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
Poznámky
Čas souboru Systému Windows je 64bitová hodnota, která představuje počet intervalů 100 nanosekund, které uplynuly od 12:00 půlnoci, 1. ledna 1601 A.D. (C.E.) Koordinovaný univerzální čas (UTC). Systém Windows používá k zaznamenávání času při vytváření, přístupu nebo zápisu aplikace do souboru.
Čas souboru systému Windows je přímo přístupný prostřednictvím rozhraní API systému Windows voláním funkce GetFileTime, která vrací FILETIME strukturu. Jedním parametrem funkce je popisovač souboru, jehož informace o čase souboru se mají načíst. Popisovač souboru se načte voláním funkce CreateFile. Člen struktury FILETIMEdwHighDateTime obsahuje čtyři bajty s vysokým pořadím času souboru a jeho dwLowDateTime člen obsahuje čtyři bajty s nízkým pořadím. Následující příklad ukazuje, jak načíst hodnoty času souboru systému Windows a převést je na DateTimeOffset hodnoty.
Hodnoty času souboru systému Windows lze vytvořit také z DateTime hodnot voláním metod DateTime.ToFileTime a DateTime.ToFileTimeUtc a z DateTimeOffset hodnot voláním metody DateTimeOffset.ToFileTime.
Platí pro
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