Directory.GetLastWriteTimeUtc(String) Metoda

Definice

Obor názvů:

System.IO

Sestavení:

System.Runtime.dll

Zdroj:

Directory.cs

Vrátí datum a čas ve formátu UTC (Coordinated Universal Time), do kterého byl zadaný soubor nebo adresář naposledy zapsán.

public:
 static DateTime GetLastWriteTimeUtc(System::String ^ path);

public static DateTime GetLastWriteTimeUtc (string path);

static member GetLastWriteTimeUtc : string -> DateTime

Public Shared Function GetLastWriteTimeUtc (path As String) As DateTime

Parametry

path

String

Soubor nebo adresář, pro který chcete získat informace o datu a čase změny.

Návraty

DateTime

Struktura, která je nastavena na datum a čas, do kterého byl zadaný soubor nebo adresář naposledy zapsán. Tato hodnota je vyjádřena v čase UTC.

Výjimky

UnauthorizedAccessException

Volající nemá požadované oprávnění.

ArgumentException

.NET Framework a .NET Core verze starší než 2.1: path je řetězec nulové délky, obsahuje pouze prázdné znaky nebo obsahuje jeden nebo více neplatných znaků. Pomocí metody můžete zadat dotaz na neplatné znaky GetInvalidPathChars() .

ArgumentNullException

path je null.

PathTooLongException

Zadaná cesta, název souboru nebo obojí překračují maximální délku definovanou systémem.

Příklady

Následující příklad ukazuje rozdíly ve výstupu při použití výstupu koordinovaného univerzálního času (UTC).

// This sample shows the differences between dates from methods that use
//coordinated universal time (UTC) format and those that do not.
using namespace System;
using namespace System::IO;
int main()
{
   
   // Set the directory.
   String^ n = "C:\\test\\newdir";
   
   //Create two variables to use to set the time.
   DateTime dtime1 = DateTime(2002,1,3);
   DateTime dtime2 = DateTime(1999,1,1);
   
   //Create the directory.
   try
   {
      Directory::CreateDirectory( n );
   }
   catch ( IOException^ e ) 
   {
      Console::WriteLine( e );
   }

   
   //Set the creation and last access times to a variable DateTime value.
   Directory::SetCreationTime( n, dtime1 );
   Directory::SetLastAccessTimeUtc( n, dtime1 );
   
   // Print to console the results.
   Console::WriteLine( "Creation Date: {0}", Directory::GetCreationTime( n ) );
   Console::WriteLine( "UTC creation Date: {0}", Directory::GetCreationTimeUtc( n ) );
   Console::WriteLine( "Last write time: {0}", Directory::GetLastWriteTime( n ) );
   Console::WriteLine( "UTC last write time: {0}", Directory::GetLastWriteTimeUtc( n ) );
   Console::WriteLine( "Last access time: {0}", Directory::GetLastAccessTime( n ) );
   Console::WriteLine( "UTC last access time: {0}", Directory::GetLastAccessTimeUtc( n ) );
   
   //Set the last write time to a different value.
   Directory::SetLastWriteTimeUtc( n, dtime2 );
   Console::WriteLine( "Changed last write time: {0}", Directory::GetLastWriteTimeUtc( n ) );
}

// Obviously, since this sample deals with dates and times, the output will vary
// depending on when you run the executable. Here is one example of the output:
//Creation Date: 1/3/2002 12:00:00 AM
//UTC creation Date: 1/3/2002 8:00:00 AM
//Last write time: 12/31/1998 4:00:00 PM
//UTC last write time: 1/1/1999 12:00:00 AM
//Last access time: 1/2/2002 4:00:00 PM
//UTC last access time: 1/3/2002 12:00:00 AM
//Changed last write time: 1/1/1999 12:00:00 AM

// This sample shows the differences between dates from methods that use
//coordinated universal time (UTC) format and those that do not.
using System;
using System.IO;

namespace IOSamples
{
  public class DirectoryUTCTime
  {
    public static void Main()
    {
    // Set the directory.
      string n = @"C:\test\newdir";
        //Create two variables to use to set the time.
      DateTime dtime1 = new DateTime(2002, 1, 3);
      DateTime dtime2 = new DateTime(1999, 1, 1);

    //Create the directory.
      try
      {
          Directory.CreateDirectory(n);
      }
      catch (IOException e)
      {
          Console.WriteLine(e);
      }

    //Set the creation and last access times to a variable DateTime value.
      Directory.SetCreationTime(n, dtime1);
      Directory.SetLastAccessTimeUtc(n, dtime1);

        // Print to console the results.
      Console.WriteLine("Creation Date: {0}", Directory.GetCreationTime(n));
      Console.WriteLine("UTC creation Date: {0}", Directory.GetCreationTimeUtc(n));
      Console.WriteLine("Last write time: {0}", Directory.GetLastWriteTime(n));
      Console.WriteLine("UTC last write time: {0}", Directory.GetLastWriteTimeUtc(n));
      Console.WriteLine("Last access time: {0}", Directory.GetLastAccessTime(n));
      Console.WriteLine("UTC last access time: {0}", Directory.GetLastAccessTimeUtc(n));

        //Set the last write time to a different value.
      Directory.SetLastWriteTimeUtc(n, dtime2);
      Console.WriteLine("Changed last write time: {0}", Directory.GetLastWriteTimeUtc(n));
    }
  }
}
// Obviously, since this sample deals with dates and times, the output will vary
// depending on when you run the executable. Here is one example of the output:
//Creation Date: 1/3/2002 12:00:00 AM
//UTC creation Date: 1/3/2002 8:00:00 AM
//Last write time: 12/31/1998 4:00:00 PM
//UTC last write time: 1/1/1999 12:00:00 AM
//Last access time: 1/2/2002 4:00:00 PM
//UTC last access time: 1/3/2002 12:00:00 AM
//Changed last write time: 1/1/1999 12:00:00 AM

// This sample shows the differences between dates from methods that use
//coordinated universal time (UTC) format and those that do not.
open System
open System.IO

// Set the directory.
let n = @"C:\test\newdir"
//Create two variables to use to set the time.
let dtime1 = DateTime(2002, 1, 3)
let dtime2 = DateTime(1999, 1, 1)

//Create the directory.
try
    Directory.CreateDirectory n |> ignore
with :? IOException as e ->
    printfn $"{e}"

//Set the creation and last access times to a variable DateTime value.
Directory.SetCreationTime(n, dtime1)
Directory.SetLastAccessTimeUtc(n, dtime1)

// Print to console the results.
printfn $"Creation Date: {Directory.GetCreationTime n}"
printfn $"UTC creation Date: {Directory.GetCreationTimeUtc n}"
printfn $"Last write time: {Directory.GetLastWriteTime n}"
printfn $"UTC last write time: {Directory.GetLastWriteTimeUtc n}"
printfn $"Last access time: {Directory.GetLastAccessTime n}"
printfn $"UTC last access time: {Directory.GetLastAccessTimeUtc n}"

//Set the last write time to a different value.
Directory.SetLastWriteTimeUtc(n, dtime2)
printfn $"Changed last write time: {Directory.GetLastWriteTimeUtc n}"
// Obviously, since this sample deals with dates and times, the output will vary
// depending on when you run the executable. Here is one example of the output:
//Creation Date: 1/3/2002 12:00:00 AM
//UTC creation Date: 1/3/2002 8:00:00 AM
//Last write time: 12/31/1998 4:00:00 PM
//UTC last write time: 1/1/1999 12:00:00 AM
//Last access time: 1/2/2002 4:00:00 PM
//UTC last access time: 1/3/2002 12:00:00 AM
//Changed last write time: 1/1/1999 12:00:00 AM

' This sample shows the differences between dates from methods that use
'coordinated universal time (UTC) format and those that do not.
Imports System.IO



Public Class DirectoryUTCTime
   
   Public Shared Sub Main()
      ' Set the directory.
      Dim n As String = "C:\test\newdir"
      'Create two variables to use to set the time.
      Dim dtime1 As New DateTime(2002, 1, 3)
      Dim dtime2 As New DateTime(1999, 1, 1)
      
      'Create the directory.
      Try
         Directory.CreateDirectory(n)
      Catch e As IOException
         Console.WriteLine(e)
      End Try
      
      'Set the creation and last access times to a variable DateTime value.
      Directory.SetCreationTime(n, dtime1)
      Directory.SetLastAccessTimeUtc(n, dtime1)
      
      ' Print to console the results.
      Console.WriteLine("Creation Date: {0}", Directory.GetCreationTime(n))
      Console.WriteLine("UTC creation Date: {0}", Directory.GetCreationTimeUtc(n))
      Console.WriteLine("Last write time: {0}", Directory.GetLastWriteTime(n))
      Console.WriteLine("UTC last write time: {0}", Directory.GetLastWriteTimeUtc(n))
      Console.WriteLine("Last access time: {0}", Directory.GetLastAccessTime(n))
      Console.WriteLine("UTC last access time: {0}", Directory.GetLastAccessTimeUtc(n))
      
      'Set the last write time to a different value.
      Directory.SetLastWriteTimeUtc(n, dtime2)
      Console.WriteLine("Changed last write time: {0}", Directory.GetLastWriteTimeUtc(n))
   End Sub
End Class

' Since this sample deals with dates and times, the output will vary
' depending on when you run the executable. Here is one example of the output:

' Creation Date: 1/3/2002 12:00:00 AM
' UTC creation Date: 1/3/2002 8:00:00 AM
' Last write time: 12/31/1998 4:00:00 PM
' UTC last write time: 1/1/1999 12:00:00 AM
' Last access time: 1/2/2002 4:00:00 PM
' UTC last access time: 1/3/2002 12:00:00 AM
' Changed last write time: 1/1/1999 12:00:00 AM

Poznámky

Poznámka

Tato metoda může vrátit nepřesnou hodnotu, protože používá nativní funkce, jejichž hodnoty nemusí být průběžně aktualizovány operačním systémem.

Pokud adresář popsaný v parametru path neexistuje, vrátí tato metoda 12:00 půlnoc, 1. ledna 1601 N.D. (C.E.) Koordinovaný univerzální čas (UTC)

Seznam běžných vstupně-výstupních úloh najdete v tématu Běžné vstupně-výstupní úlohy.

Viz také

• FileSystemWatcher
• Vstupně-výstupní operace souborů a Stream
• Postupy: Čtení textu ze souboru
• Postupy: Zápis textu do souboru