FileInfo.Open 方法

定义

命名空间:: System.IO

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

程序集:: mscorlib.dll

程序集:: System.IO.FileSystem.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

打开具有各种读取/写入和共享权限的文件。

重载

名称	说明
Open(FileMode)	在指定模式下打开文件。
Open(FileMode, FileAccess)	在指定模式下打开具有读取、写入或读/写访问权限的文件。
Open(FileMode, FileAccess, FileShare)	在指定的模式下打开具有读取、写入或读/写访问权限和指定共享选项的文件。

Open(FileMode)

在指定模式下打开文件。

public:
 System::IO::FileStream ^ Open(System::IO::FileMode mode);

public System.IO.FileStream Open(System.IO.FileMode mode);

member this.Open : System.IO.FileMode -> System.IO.FileStream

Public Function Open (mode As FileMode) As FileStream

参数

mode: FileMode

一个 FileMode 常量，用于指定打开文件的模式（例如， Open 或 Append）。

FileStream

在指定模式下打开的文件，具有读/写访问权限和未共享权限。

例外

FileNotFoundException

找不到该文件。

UnauthorizedAccessException

该文件为只读文件或目录。

DirectoryNotFoundException

指定的路径无效，例如在未映射的驱动器上。

IOException

该文件已打开。

示例

以下示例打开一个文件，向该文件添加一些信息，并读取该文件。

using System;
using System.IO;
using System.Text;

class Test
{
    
    public static void Main()
    {
        string path = @"c:\MyTest.txt";
        FileInfo fi = new FileInfo(path);

        // Delete the file if it exists.
        if (!fi.Exists)
        {
            //Create the file.
            using (FileStream fs = fi.Create())
            {
                Byte[] info = new UTF8Encoding(true).GetBytes("This is some text in the file.");
                //Add some information to the file.
                fs.Write(info, 0, info.Length);
            }
        }

        //Open the stream and read it back.
        using (FileStream fs = fi.Open(FileMode.Open))
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);
            while (fs.Read(b,0,b.Length) > 0)
            {
                Console.WriteLine(temp.GetString(b));
            }
        }
    }
}
//This code produces output similar to the following;
//results may vary based on the computer/file structure/etc.:
//
//This is some text in the file.
//
//
//
//
//
//
//
//
//
//
//
//

Imports System.IO
Imports System.Text

Public Class Test

    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"
        Dim fi As FileInfo = New FileInfo(path)
        Dim fs As FileStream

        ' Delete the file if it exists.
        If fi.Exists = False Then
            'Create the file.
            fs = fi.Create()
            Dim info As Byte() = New UTF8Encoding(True).GetBytes("This is some text in the file.")
            'Add some information to the file.
            fs.Write(info, 0, info.Length)
            fs.Close()
        End If

        'Open the stream and read it back.
        fs = fi.Open(FileMode.Open)
        Dim b(1023) As Byte
        Dim temp As UTF8Encoding = New UTF8Encoding(True)
        Do While fs.Read(b, 0, b.Length) > 0
            Console.WriteLine(temp.GetString(b))
        Loop
        fs.Close()
    End Sub
End Class
'This code produces output similar to the following; 
'results may vary based on the computer/file structure/etc.:
'
'This is some text in the file.
'
'
'
'
'
'
'
'
'
'
'
'

另请参阅

适用于

Open(FileMode, FileAccess)

在指定模式下打开具有读取、写入或读/写访问权限的文件。

public:
 System::IO::FileStream ^ Open(System::IO::FileMode mode, System::IO::FileAccess access);

public System.IO.FileStream Open(System.IO.FileMode mode, System.IO.FileAccess access);

member this.Open : System.IO.FileMode * System.IO.FileAccess -> System.IO.FileStream

Public Function Open (mode As FileMode, access As FileAccess) As FileStream

参数

mode: FileMode

一个 FileMode 常量，用于指定打开文件的模式（例如， Open 或 Append）。

access: FileAccess

一个FileAccess常量，指定是使用Read文件WriteReadWrite访问还是文件访问打开文件。

FileStream

FileStream在指定的模式和访问权限中打开的对象，以及取消共享的对象。

例外

SecurityException

调用方没有所需的权限。

FileNotFoundException

找不到该文件。

UnauthorizedAccessException

Name 为只读或目录。

DirectoryNotFoundException

指定的路径无效，例如在未映射的驱动器上。

IOException

该文件已打开。

ArgumentException

Name 为空或仅包含空格。

ArgumentNullException

一个或多个参数为 null。

示例

以下示例将文件作为只读打开，并从该文件中读取。

using System;
using System.IO;
using System.Text;

class Test
{
    
    public static void Main()
    {
        string path = @"c:\MyTest.txt";
        FileInfo fi = new FileInfo(path);

        // Delete the file if it exists.
        if (!fi.Exists)
        {
            //Create the file.
            using (FileStream fs = fi.Create())
            {
                Byte[] info = new UTF8Encoding(true).GetBytes("This is some text in the file.");
                //Add some information to the file.
                fs.Write(info, 0, info.Length);
            }
        }

        //Open the stream and read it back.
        using (FileStream fs = fi.Open(FileMode.Open, FileAccess.Read))
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);
            while (fs.Read(b,0,b.Length) > 0)
            {
                Console.WriteLine(temp.GetString(b));
            }

            try
            {
                //Try to write to the file.
                fs.Write(b,0,b.Length);
            }
            catch (Exception e)
            {
                Console.WriteLine("Writing was disallowed, as expected: {0}",
                    e.ToString());
            }
        }
    }
}
//This code produces output similar to the following;
//results may vary based on the computer/file structure/etc.:
//
//This is some text in the file.
//
//
//
//
//
//
//
//
//
//
//
//
//Writing was disallowed, as expected: System.NotSupportedException: Stream does
//not support writing.
//   at System.IO.__Error.WriteNotSupported()
//   at System.IO.FileStream.Write(Byte[] array, Int32 offset, Int32 count)
//   at Test.Main() in C:\Documents and Settings\My Computer\My Documents\
//Visual Studio 2005\Projects\finfo open2\finfo open2\Program.cs:line 39

imports System.IO
imports System.Text

Public Class Test
    Public Shared Sub Main()
        Dim path As String = "c:\MyTest.txt"
        Dim fi As FileInfo = new FileInfo(path)
        Dim fs As FileStream

        ' Delete the file if it exists.
        If fi.Exists = False
            'Create the file.
            fs = fi.Create()
            Dim info As Byte() = _
                    New UTF8Encoding(true).GetBytes( _
                        "This is some text in the file.")

            'Add some information to the file.
            fs.Write(info, 0, info.Length)
            fs.Close()
        End If

        'Open the stream and read it back.
        fs = fi.Open(FileMode.Open, FileAccess.Read)
        Dim b(1023) As byte
        Dim temp As UTF8Encoding = New UTF8Encoding(true)

        Do While fs.Read(b,0,b.Length) > 0
            Console.WriteLine(temp.GetString(b))
        Loop
            Try
                fs.Write(b,0,b.Length)
                Catch e As Exception
                Console.WriteLine("Writing was disallowed, as expected: {0}", e.ToString())
            End Try
        fs.Close()
    End Sub
End Class
'This code produces output similar to the following; 
'results may vary based on the computer/file structure/etc.:
'
'This is some text in the file.
'
'
'
'
'
'
'
'
'
'
'
'
'Writing was disallowed, as expected: System.NotSupportedException: Stream does 
'not support writing.
'   at System.IO.__Error.WriteNotSupported()
'   at System.IO.FileStream.Write(Byte[] array, Int32 offset, Int32 count)
'   at VB_Console_Application.Test.Main() in C:\Documents and Settings\MyComputer
'\My Documents\Visual Studio 2005\Projects\finfo open2\finfo open2\Module1.vb:line 34
'

另请参阅

适用于

Open(FileMode, FileAccess, FileShare)

在指定的模式下打开具有读取、写入或读/写访问权限和指定共享选项的文件。

public:
 System::IO::FileStream ^ Open(System::IO::FileMode mode, System::IO::FileAccess access, System::IO::FileShare share);

public System.IO.FileStream Open(System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share);

member this.Open : System.IO.FileMode * System.IO.FileAccess * System.IO.FileShare -> System.IO.FileStream

Public Function Open (mode As FileMode, access As FileAccess, share As FileShare) As FileStream

参数

mode: FileMode

一个 FileMode 常量，用于指定打开文件的模式（例如， Open 或 Append）。

access: FileAccess

一个FileAccess常量，指定是使用Read文件WriteReadWrite访问还是文件访问打开文件。

share: FileShare

指定 FileShare 其他 FileStream 对象对此文件具有的访问类型的常量。

FileStream

FileStream使用指定的模式、访问和共享选项打开的对象。

例外

SecurityException

调用方没有所需的权限。

FileNotFoundException

找不到该文件。

UnauthorizedAccessException

Name 为只读或目录。

DirectoryNotFoundException

指定的路径无效，例如在未映射的驱动器上。

IOException

该文件已打开。

ArgumentException

Name 为空或仅包含空格。

ArgumentNullException

一个或多个参数为 null。

示例

以下示例演示如何打开文件进行读取和写入，但不允许访问其他用户或进程。

using System;
using System.IO;

public class OpenTest
{
    public static void Main()
    {
        // Open an existing file, or create a new one.
        FileInfo fi = new FileInfo("temp.txt");

        // Open the file just specified such that no one else can use it.
        FileStream fs = fi.Open( FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None );

        // Create another reference to the same file.
        FileInfo nextfi = new FileInfo("temp.txt");

        try
        {
            // Try opening the same file, which was locked by the previous process.
            nextfi.Open( FileMode.OpenOrCreate, FileAccess.Read );

            Console.WriteLine("The file was not locked, and was opened by a second process.");
        }
        catch (IOException)
        {
            Console.WriteLine("The file could not be opened because it was locked by another process.");
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }

        // Close the file so it can be deleted.
        fs.Close();
    }
}

//This code produces output similar to the following;
//results may vary based on the computer/file structure/etc.:
//
//The file could not be opened because it was locked by another process.

Imports System.IO

Public Class OpenTest

    Public Shared Sub Main()
        ' Open an existing file, or create a new one.
        Dim fi As New FileInfo("temp.txt")

        ' Open the file just specified such that no one else can use it.
        Dim fs As FileStream = fi.Open(FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None)

        ' Create another reference to the same file.
        Dim nextfi As New FileInfo("temp.txt")

        Try
            ' Try opening the same file, which was locked by the previous process.
            nextfi.Open(FileMode.OpenOrCreate, FileAccess.Read)
            Console.WriteLine("The file was not locked, and was opened by a second process.")
        Catch i as IOException
            Console.WriteLine(i.ToString())
        Catch e As Exception
            Console.WriteLine(e.ToString())
        End Try

        ' Close the file so it can be deleted.
        fs.Close()
    End Sub
End Class
'This code produces output similar to the following; 
'results may vary based on the computer/file structure/etc.:
'
'System.IO.IOException: The process cannot access the file 
''C:\Documents and Settings\mydirectory\My Documents\Visual Studio 2005
'\Projects\fileinfoopen\fileinfoopen\obj\Release\temp.txt' 
'because it is being used by another process.
'at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
'at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, 
'Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions
'options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
'at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access,
'FileShare share) at System.IO.FileInfo.Open(FileMode mode, FileAccess access)
'at VB_Console_Application.OpenTest.Main() in C:\Documents and Settings
'\mydirectory\My Documents\Visual Studio 2005\Projects\VB_Console_Application
'\VB_Console_Application\Module1.vb:line 19

另请参阅

适用于

反馈

此页面是否有帮助？

FileInfo.Open 方法

定义

重载

Open(FileMode)

参数

返回

例外

示例

另请参阅

适用于

Open(FileMode, FileAccess)

参数

返回

例外

示例

另请参阅

适用于

Open(FileMode, FileAccess, FileShare)

参数

返回

例外

示例

另请参阅

适用于