FileOptions 枚举

定义

表示用于创建 FileStream 对象的高级选项。Represents advanced options for creating a FileStream object.

此枚举有一个 FlagsAttribute 属性,允许按位组合成员值。

public enum class FileOptions
[System.Flags]
[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public enum FileOptions
type FileOptions = 
Public Enum FileOptions
继承
FileOptions
属性

字段

Asynchronous 1073741824

指示文件可用于异步读取和写入。Indicates that a file can be used for asynchronous reading and writing.

DeleteOnClose 67108864

指示当不再使用某个文件时,自动删除该文件。Indicates that a file is automatically deleted when it is no longer in use.

Encrypted 16384

指示文件是加密的,只能通过用于加密的同一用户帐户来解密。Indicates that a file is encrypted and can be decrypted only by using the same user account used for encryption.

None 0

指示在生成 FileStream 对象时,不应使用其他选项。Indicates that no additional options should be used when creating a FileStream object.

RandomAccess 268435456

指示随机访问文件。Indicates that the file is accessed randomly. 系统可将此选项用作优化文件缓存的提示。The system can use this as a hint to optimize file caching.

SequentialScan 134217728

指示按从头到尾的顺序访问文件。Indicates that the file is to be accessed sequentially from beginning to end. 系统可将此选项用作优化文件缓存的提示。The system can use this as a hint to optimize file caching. 如果应用程序移动用于随机访问的文件指针,可能不发生优化缓存,但仍然保证操作的正确性。If an application moves the file pointer for random access, optimum caching may not occur; however, correct operation is still guaranteed. 如果指定此标志,可提升某些案例中的性能。Specifying this flag can increase performance in some cases.

WriteThrough -2147483648

指示系统应通过任何中间缓存、直接写入磁盘。Indicates that the system should write through any intermediate cache and go directly to disk.

示例

下面的示例演示如何在创建文件流时使用异步值。The following example shows how to use the Asynchronous value when creating a file stream.

using System;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            WriteToFile();
        }

        static async void WriteToFile()
        {
            byte[] bytesToWrite = Encoding.Unicode.GetBytes("example text to write");
            using (FileStream createdFile = File.Create("c:/Temp/testfile.txt", 4096, FileOptions.Asynchronous))
            {
                await createdFile.WriteAsync(bytesToWrite, 0, bytesToWrite.Length);
            }
        }
    }
}
Imports System.IO
Imports System.Text

Module Module1

    Sub Main()
        WriteToFile()
    End Sub

    Async Sub WriteToFile()
        Dim bytesToWrite = Encoding.Unicode.GetBytes("example text to write")
        Using createdFile As FileStream = File.Create("c:/Temp/testfile.txt", 4096, FileOptions.Asynchronous)
            Await createdFile.WriteAsync(bytesToWrite, 0, bytesToWrite.Length)
        End Using
    End Sub

End Module

注解

指定 FileOptions.SequentialScan 标志可以提高使用顺序访问读取大型文件的应用程序的性能。Specifying the FileOptions.SequentialScan flag can increase performance for applications that read large files using sequential access. 对于经常按顺序读取大型文件的应用程序,性能提升更为明显,但偶尔会跳过小范围的字节。Performance gains can be even more noticeable for applications that read large files mostly sequentially, but occasionally skip over small ranges of bytes.

适用于