FileSystemInfo.LastWriteTime 属性

定义

命名空间:
System.IO
程序集:
System.IO.FileSystem.dll, mscorlib.dll, netstandard.dll

获取或设置上次写入当前文件或目录的时间。Gets or sets the time when the current file or directory was last written to.

public:
 property DateTime LastWriteTime { DateTime get(); void set(DateTime value); };
public DateTime LastWriteTime { get; set; }
member this.LastWriteTime : DateTime with get, set
Public Property LastWriteTime As DateTime

属性值

DateTime

上次写入当前文件的时间。The time the current file was last written.

异常

IOException

Refresh() 不能初始化数据。Refresh() cannot initialize the data.

PlatformNotSupportedException

当前操作系统不是 Windows NT 或更高版本。The current operating system is not Windows NT or later.

ArgumentOutOfRangeException

调用方试图设置无效的写入时间。The caller attempts to set an invalid write time.

示例

下面的代码示例演示如何通过 "touch LastWriteTime " 操作更新属性。The following code example demonstrates the updating of the LastWriteTime property through a "touch" operation. 在此示例中, 该文件将被 "触摸", CreationTime LastAccessTime并将LastWriteTime和属性更新为当前日期和时间。In this example, the file is "touched", updating the CreationTime, LastAccessTime and LastWriteTime properties to the current date and time.

using System;
using System.IO;

namespace touch
{
    class Touch
    {
        static void Main(string[] args)
        {
            // Make sure a filename was provided.
            if (args.Length > 0)
            {
                // Verify that the provided filename exists.
                if (File.Exists(args[0]))
                {
                    FileInfo fi = new FileInfo(args[0]);
                    touchFile(fi);
                }
                else
                {
                    Console.WriteLine(
                        "Could not find the file: {0}.", args[0]);
                }
            }
            else
            {
                Console.WriteLine("No file was specified.");
            }
        }

        static void touchFile(FileSystemInfo fsi)
        {
            Console.WriteLine("Touching: {0}", fsi.FullName);

            // Update the CreationTime, LastWriteTime and LastAccessTime.
            try
            {
                fsi.CreationTime = fsi.LastWriteTime = fsi.LastAccessTime =
                    DateTime.Now;
            }
            catch (Exception e)
            {
                Console.WriteLine("Error: {0}", e.Message);
            }
        }
    }
}

Imports System.IO

Public Class Touch
    Public Shared Sub Main(ByVal args() As String)

        ' Make sure an argument (filename) was provided.
        If args.Length > 0 Then

            ' Verify that the provided filename exists.
            If File.Exists(args(0)) Then
                Dim fi As FileInfo = New FileInfo(args(0))
                touchFile(fi)
            Else
                Console.WriteLine("Could not find the file {0}", args(0))
            End If
        Else
            Console.WriteLine("No file specified.")
        End If
    End Sub

    Public Shared Sub touchFile(ByVal fsi As FileSystemInfo)
        Console.WriteLine("Touching: {0}", fsi.FullName)

        ' Update the CreationTime, LastWriteTime and LastAccessTime.
        Try
            fsi.CreationTime = DateTime.Now
            fsi.LastAccessTime = DateTime.Now
            fsi.LastWriteTime = DateTime.Now
        Catch e As Exception
            Console.WriteLine("Error: {0}", e.Message)
        End Try

    End Sub

End Class

注解

备注

此方法可能会返回不正确的值, 因为它使用的本机函数的值可能不会持续由操作系统进行更新。This method may return an inaccurate value because it uses native functions whose values may not be continuously updated by the operating system.

如果FileSystemInfo对象的当前LastWriteTime实例是从以下DirectoryInfo任一方法返回的, 则该属性的值将被预先缓存:The value of the LastWriteTime property is pre-cached if the current instance of the FileSystemInfo object was returned from any of the following DirectoryInfo methods:

若要获取最新值, 请Refresh调用方法。To get the latest value, call the Refresh method.

如果FileSystemInfo对象中描述的文件或目录不存在, 或者包含此文件或目录的文件系统不支持此信息, 则此属性将返回12:00 年1月1日午夜1601If the file or directory described in the FileSystemInfo object does not exist, or if the file system that contains this file or directory does not support this information, this property returns 12:00 midnight, January 1, 1601 A.D. 公元协调世界时 (UTC), 调整为本地时间。(C.E.) Coordinated Universal Time (UTC), adjusted to local time.

安全性

FileIOPermission
用于设置上次写入时间。for setting the last write time. 关联的枚举:WriteAssociated enumeration: Write

适用于

另请参阅