File.GetLastWriteTime 方法

参考

定义

命名空间:: System.IO

程序集:: mscorlib.dll, System.IO.FileSystem.dll

程序集:: System.IO.FileSystem.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

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重载

GetLastWriteTime(String)	返回上次写入指定文件或目录的日期和时间。
GetLastWriteTime(SafeFileHandle)	返回指定文件或目录的上次写入日期和时间。

GetLastWriteTime(String)

返回上次写入指定文件或目录的日期和时间。

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

public static DateTime GetLastWriteTime (string path);

static member GetLastWriteTime : string -> DateTime

Public Shared Function GetLastWriteTime (path As String) As DateTime

参数

path: String

要获取其写入日期和时间信息的文件或目录。

DateTime

一个 DateTime 结构，它被设置为上次写入指定文件或目录的日期和时间。该值用本地时间表示。

例外

UnauthorizedAccessException

调用方没有所要求的权限。

ArgumentException

.NET Framework 和 .NET Core 版本早于 2.1： path 是零长度字符串，仅包含空格，或包含一个或多个无效字符。你可以使用 GetInvalidPathChars() 方法查询无效字符。

ArgumentNullException

path 为 null。

PathTooLongException

指定的路径和/或文件名超过了系统定义的最大长度。

NotSupportedException

path 的格式无效。

示例

下面的示例演示 GetLastWriteTime。

using namespace System;
using namespace System::IO;
int main()
{
   try
   {
      String^ path = "c:\\Temp\\MyTest.txt";
      if (  !File::Exists( path ) )
      {
         File::Create( path );
      }
      else
      {
         
         // Take an action that will affect the write time.
         File::SetLastWriteTime( path, DateTime(1985,4,3) );
      }
      
      // Get the creation time of a well-known directory.
      DateTime dt = 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 ( Exception^ e ) 
   {
      Console::WriteLine( "The process failed: {0}", e );
   }

}

using System;
using System.IO;

class Test
{
    public static void Main()
    {
        try
        {
            string path = @"c:\Temp\MyTest.txt";
            if (!File.Exists(path))
            {
                File.Create(path);
            }
            else
            {
                // Take an action that will affect the write time.
                File.SetLastWriteTime(path, new DateTime(1985,4,3));
            }

            // Get the creation time of a well-known directory.
            DateTime dt = 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 (Exception e)
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    }
}

open System
open System.IO

let path = @"c:\Temp\MyTest.txt"

if File.Exists path |> not then
    File.Create path |> ignore
else
    // Take an action that will affect the write time.
    File.SetLastWriteTime(path, DateTime(1985, 4, 3))

// Get the creation time of a well-known directory.
let dt = File.GetLastWriteTime path
printfn $"The last write time for this file was {dt}."

// Update the last write time.
File.SetLastWriteTime(path, DateTime.Now)
let dt2 = File.GetLastWriteTime path
printfn $"The last write time for this file was {dt2}."

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

注解

注意

此方法可能返回不准确的值，因为它使用本机函数，其值可能不会由操作系统持续更新。每个操作系统根据自己的规则管理上次写入时间。为了提高性能，操作系统可能不会将上次写入时间值设置为上次写入操作的确切时间，而是将其设置为接近近似值。

如果参数中描述的 path 文件不存在，则此方法返回 1601 年 1 月 1 日午夜 12：00,00， (C.E.) 协调世界时 (UTC) ，调整为本地时间。

允许 path 参数指定相对路径信息或绝对路径信息。相对路径信息被解释为相对于当前工作目录。若要获取当前工作目录，请参阅 GetCurrentDirectory。

有关常见 I/O 任务的列表，请参阅常见 I/O 任务。

另请参阅

适用于

GetLastWriteTime(SafeFileHandle)

返回指定文件或目录的上次写入日期和时间。

public:
 static DateTime GetLastWriteTime(Microsoft::Win32::SafeHandles::SafeFileHandle ^ fileHandle);

public static DateTime GetLastWriteTime (Microsoft.Win32.SafeHandles.SafeFileHandle fileHandle);

static member GetLastWriteTime : Microsoft.Win32.SafeHandles.SafeFileHandle -> DateTime

Public Shared Function GetLastWriteTime (fileHandle As SafeFileHandle) As DateTime

参数

fileHandle: SafeFileHandle

要 SafeFileHandle 获取上次写入日期和时间信息的文件或目录的。