DateTime.ToFileTime Method

Reference

Definition

Namespace:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: DateTime.cs

Source:: DateTime.cs

Source:: DateTime.cs

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 value of the current DateTime object to a Windows file time.

public:
 long ToFileTime();

public long ToFileTime ();

member this.ToFileTime : unit -> int64

Public Function ToFileTime () As Long

Returns

Int64

The value of the current DateTime object expressed as a Windows file time.

Exceptions

ArgumentOutOfRangeException

The resulting file time would represent a date and time before 12:00 midnight January 1, 1601 C.E. UTC.

Examples

The following example demonstrates the ToFileTime method.

int main()
{
   System::Console::WriteLine( "Enter the file path:" );
   String^ filePath = System::Console::ReadLine();
   if ( System::IO::File::Exists( filePath ) )
   {
      System::DateTime fileCreationDateTime = System::IO::File::GetCreationTime( filePath );
      __int64 fileCreationFileTime = fileCreationDateTime.ToFileTime();
      System::Console::WriteLine( "{0} in file time is {1}.", fileCreationDateTime, fileCreationFileTime );
   }
   else
   {
      System::Console::WriteLine( "{0} is an invalid file", filePath );
   }
}

open System.IO

printfn "Enter the file path:"
let filePath = stdin.ReadLine()

if File.Exists filePath then
    let fileCreationDateTime =
        File.GetCreationTime filePath

    let fileCreationFileTime = fileCreationDateTime.ToFileTime()

    printfn $"{fileCreationDateTime} in file time is {fileCreationFileTime}."

else
    printfn $"{filePath} is an invalid file"

static void Main(string[] args)
{
    System.Console.WriteLine("Enter the file path:");
    string filePath = System.Console.ReadLine();

    if (System.IO.File.Exists(filePath)) {
        System.DateTime fileCreationDateTime =
            System.IO.File.GetCreationTime(filePath);

        long fileCreationFileTime = fileCreationDateTime.ToFileTime();

        System.Console.WriteLine("{0} in file time is {1}.",
                                 fileCreationDateTime,
                                 fileCreationFileTime);
    }
    else {
        System.Console.WriteLine("{0} is an invalid file", filePath);
    }
}

Public Shared Sub Main()

   System.Console.WriteLine("Enter the file path:")
   Dim filePath As String
   filePath = System.Console.ReadLine()

   If System.IO.File.Exists(filePath) Then
      Dim fileCreationDateTime As System.DateTime
      fileCreationDateTime = System.IO.File.GetCreationTime(filePath)

      Dim fileCreationFileTime As Long
      fileCreationFileTime = fileCreationDateTime.ToFileTime()

      System.Console.WriteLine("{0} in file time is {1}.", _
                               fileCreationDateTime, _
                               fileCreationFileTime)
   Else
      System.Console.WriteLine("{0} is an invalid file", filePath)
   End If
End Sub

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.

The ToFileTime method uses the Kind property to determine whether the current DateTime object is a local time, a UTC time, or an unspecified kind of time which is treated as a local time.

Notes to Callers

Ordinarily, the FromFileTime(Int64) method restores a DateTime value that was saved by the ToFileTime() method. However, the two values may differ under the following conditions:

If the serialization and deserialization of the DateTime value occur in different time zones. For example, if a DateTime value with a time of 12:30 P.M. in the U.S. Eastern Time zone is serialized, and then deserialized in the U.S. Pacific Time zone, the original value of 12:30 P.M. is adjusted to 9:30 A.M. to reflect the difference between the two time zones.

If the DateTime value that is serialized represents an invalid time in the local time zone. In this case, the ToFileTime() method adjusts the restored DateTime value so that it represents a valid time in the local time zone.

For example, the transition from standard time to daylight saving time occurs in the U.S. Pacific Time zone on March 14, 2010, at 2:00 A.M., when the time advances by one hour, to 3:00 A.M. This hour interval is an invalid time, that is, a time interval that does not exist in this time zone. The following example shows that when a time that falls within this range is converted to a long integer value by the ToFileTime() method and is then restored by the FromFileTime(Int64) method, the original value is adjusted to become a valid time. You can determine whether a particular date and time value may be subject to modification by passing it to the IsInvalidTime(DateTime) method, as the example illustrates.

using System;

public class Example
{
   public static void Main()
   {
      DateTime date1 = new DateTime(2010, 3, 14, 2, 30, 00);
      Console.WriteLine("Invalid Time: {0}",
                        TimeZoneInfo.Local.IsInvalidTime(date1));
      long ft = date1.ToFileTime();
      DateTime date2 = DateTime.FromFileTime(ft);
      Console.WriteLine("{0} -> {1}", date1, date2);
   }
}
// The example displays the following output:
//       Invalid Time: True
//       3/14/2010 2:30:00 AM -> 3/14/2010 3:30:00 AM

open System

let date1 = DateTime(2010, 3, 14, 2, 30, 00)
printfn $"Invalid Time: {TimeZoneInfo.Local.IsInvalidTime date1}"

let ft = date1.ToFileTime()
let date2 = DateTime.FromFileTime ft
printfn $"{date1} -> {date2}"

// The example displays the following output:
//       Invalid Time: True
//       3/14/2010 2:30:00 AM -> 3/14/2010 3:30:00 AM

Module Example
   Public Sub Main()
      Dim date1 As New DateTime(2010, 3, 14, 2, 30, 00)
      Console.WriteLine("Invalid Time: {0}", TimeZoneInfo.Local.IsInvalidTime(date1))
      Dim ft As Long = date1.ToFileTime()
      Dim date2 As DateTime = DateTime.FromFileTime(ft)
      Console.WriteLine("{0} -> {1}", date1, date2) 
   End Sub
End Module
' The example displays the following output:
'       Invalid Time: True
'       3/14/2010 2:30:00 AM -> 3/14/2010 3:30:00 AM

Applies to

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