C＃中的File.SetLastWriteTimeUtc()方法与示例

File.SetLastWriteTimeUtc(String)是一个内置的File类方法，该方法用于设置指定文件最后写入的日期和时间(以协调世界时(UTC))。
句法：

public static void SetLastWriteTimeUtc (string path, DateTime lastWriteTime);

参数：该函数接受两个参数，如下所示：

• path: This is the specified file for which to set the date and time information.
• lastWriteTime: This is the specified last written date and time of the path that is expressed in UTC time.

例外情况：

• ArgumentException：路径是长度为零的字符串，仅包含空格，或者由InvalidPathChars定义的一个或多个无效字符。
• ArgumentNullException：路径为null。
• PathTooLongException：指定的路径，文件名或两者都超过系统定义的最大长度。
• FileNotFoundException：找不到指定的路径。
• UnauthorizedAccessException：调用者没有所需的权限。
• NotSupportedException：路径格式无效。
• ArgumentOutOfRangeException： lastWriteTime指定一个超出此操作允许的日期或时间范围的值。

下面是说明File.SetLastWriteTimeUtc(String，DateTime)方法的程序。
程序1：在运行下面的代码之前，将创建一个文件file.txt ，其内容如下所示：

C#

// C# program to illustrate the usage
// of File.SetLastWriteTimeUtc() method
  
// Using System and System.IO namespaces
using System;
using System.IO;
  
class GFG {
    public static void Main()
    {
        // Specifying a file
        string myfile = @"file.txt";
  
        // Calling the SetLastWriteTimeUtc() function
        // to set last written date and time in UTC
        File.SetLastWriteTimeUtc(myfile, new DateTime(2020,
                                           5, 4, 4, 5, 7));
  
        // Getting the last written date and time
        // expressed in UTC of the file
        DateTime dt = File.GetLastWriteTimeUtc(myfile);
        Console.WriteLine("The last written date and"+
           " time in UTC for this file was {0}.", dt);
    }
}

输出：

The last written date and time in UTC for this file was 5/4/2020 4:05:07 AM.

程序2：最初没有创建文件。在代码下方，其自身创建文件file.txt并打印最后写入的日期和时间。

C＃

// C# program to illustrate the usage
// of File.SetLastWriteTimeUtc() method
  
// Using System and System.IO namespaces
using System;
using System.IO;
  
class GFG {
    public static void Main()
    {
        // Specifying a file
        string path = @"file.txt";
  
        // Checking the existance of the file
        if (!File.Exists(path)) {
            File.Create(path);
        }
  
        // Calling the SetLastWriteTimeUtc() function
        // to set last written date and time in UTC
        File.SetLastWriteTimeUtc(path, new DateTime(2019,
                                         5, 4, 4, 5, 7));
  
        // Getting the last written date and time in UTC
        // of the specified file
        DateTime dt = File.GetLastWriteTimeUtc(path);
        Console.WriteLine("The last written date and time "+
                       "in UTC for this file was {0}.", dt);
    }
}

执行中：

The last written date and time in UTC for this file was 5/4/2019 4:05:07 AM.