File.Open 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

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。

打开指定路径上的 FileStream。

重载

Open(String, FileMode, FileAccess, FileShare)	打开指定路径上的 FileStream，具有带读、写或读/写访问的指定模式和指定的共享选项。
Open(String, FileMode)	通过不共享的读/写访问权限打开指定路径上的 FileStream。
Open(String, FileStreamOptions)	使用指定的路径、创建模式、读/写和共享权限、其他 FileStreams 对同一文件的访问权限、缓冲区大小、其他文件选项和分配大小初始化类的新实例 FileStream 。
Open(String, FileMode, FileAccess)	通过指定的模式和不共享的访问权限打开指定路径上的 FileStream。

Open(String, FileMode, FileAccess, FileShare)

Source:: File.cs

Source:: File.cs

Source:: File.cs

打开指定路径上的 FileStream，具有带读、写或读/写访问的指定模式和指定的共享选项。

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

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

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

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

参数

path: String

要打开的文件。

mode: FileMode

FileMode 值，用于指定在文件不存在时是否创建该文件，并确定是保留还是覆盖现有文件的内容。

access: FileAccess

一个 FileAccess 值，它指定可以对文件执行的操作。

share: FileShare

一个 FileShare 值，它指定其他线程所具有的对该文件的访问类型。

FileStream

指定路径上的 FileStream，具有带读、写或读/写访问的指定模式以及指定的共享选项。

例外

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。

- 或 -

access 指定了 Read，并且 mode 指定了 Create、CreateNew、Truncate 或 Append。

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。

DirectoryNotFoundException

指定的路径无效（例如，它位于未映射的驱动器上）。

IOException

打开文件时发生 I/O 错误。

UnauthorizedAccessException

path 指定了一个只读文件，并且 access 不是 Read。

- 或 -

path 指定了一个目录。

- 或 -

调用方没有所要求的权限。

- 或 -

mode 为 Create，指定文件为隐藏文件。

ArgumentOutOfRangeException

mode、access 或 share 指定了一个无效值。

FileNotFoundException

未找到 path 中指定的文件。

NotSupportedException

path 的格式无效。

示例

以下示例打开一个具有只读访问权限且不允许文件共享的文件。

using namespace System;
using namespace System::IO;
using namespace System::Text;

int main()
{
   String^ path = "c:\\temp\\MyTest.txt";
   
   // Create the file if it does not exist.
   if (  !File::Exists( path ) )
   {
      // Create the file.
      FileStream^ fs = File::Create( path );
      try
      {
         array<Byte>^info = (gcnew UTF8Encoding( true ))->GetBytes( "This is some text in the file." );
         
         // Add some information to the file.
         fs->Write( info, 0, info->Length );
      }
      finally
      {
         if ( fs )
                  delete (IDisposable^)fs;
      }
   }
   
   // Open the stream and read it back.
   FileStream^ fs = File::Open( path, FileMode::Open, FileAccess::Read, FileShare::None );
   try
   {
      array<Byte>^b = gcnew array<Byte>(1024);
      UTF8Encoding^ temp = gcnew UTF8Encoding( true );
      while ( fs->Read( b, 0, b->Length ) > 0 )
      {
         Console::WriteLine( temp->GetString( b ) );
      }
      try
      {
         // Try to get another handle to the same file.
         FileStream^ fs2 = File::Open( path, FileMode::Open );
         try
         {
            // Do some task here.
         }
         finally
         {
            if ( fs2 )
                        delete (IDisposable^)fs2;
         }
      }
      catch ( Exception^ e ) 
      {
         Console::Write( "Opening the file twice is disallowed." );
         Console::WriteLine( ", as expected: {0}", e );
      }
   }
   finally
   {
      if ( fs )
            delete (IDisposable^)fs;
   }
}

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

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

        // Create the file if it does not exist.
        if (!File.Exists(path))
        {
            // Create the file.
            using (FileStream fs = File.Create(path))
            {
                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 = File.Open(path, FileMode.Open, FileAccess.Read, FileShare.None))
        {
            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 get another handle to the same file.
                using (FileStream fs2 = File.Open(path, FileMode.Open))
                {
                    // Do some task here.
                }
            }
            catch (Exception e)
            {
                Console.Write("Opening the file twice is disallowed.");
                Console.WriteLine(", as expected: {0}", e.ToString());
            }
        }
    }
}

open System.IO
open System.Text

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

// Create the file if it does not exist.
if File.Exists path |> not then
    // Create the file.
    use fs = File.Create path

    let info =
        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.
do
    use fs =
        File.Open(path, FileMode.Open, FileAccess.Read, FileShare.None)

    let b = Array.zeroCreate 1024
    let temp = UTF8Encoding true

    while fs.Read(b, 0, b.Length) > 0 do
        printfn $"{temp.GetString b}"

    try
        // Try to get another handle to the same file.
        use fs2 = File.Open(path, FileMode.Open)
        // Do some task here.
        ()
    with
    | e -> printf "Opening the file twice is disallowed, as expected: {e}"

Imports System.IO
Imports System.Text

Public Class Test
  Public Shared Sub Main()
    Dim path As String = "c:\temp\MyTest.txt"

    ' Create the file if it does not exist. 
    If Not File.Exists(path) Then
      ' Create the file.
      Using fs As FileStream = File.Create(path)
        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)
      End Using
    End If

    ' Open the stream and read it back.
    Using fs As FileStream = File.Open(path, FileMode.Open, FileAccess.Read, FileShare.None)
      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
        ' Try to get another handle to the same file. 
        Using fs2 As FileStream = File.Open(path, FileMode.Open)
          ' Do some task here.
        End Using
      Catch e As Exception
        Console.Write("Opening the file twice is disallowed.")
        Console.WriteLine(", as expected: {0}", e.ToString())
      End Try

    End Using

  End Sub
End Class

注解

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

Open(String, FileMode)

Source:: File.cs

Source:: File.cs

Source:: File.cs

通过不共享的读/写访问权限打开指定路径上的 FileStream。

public:
 static System::IO::FileStream ^ Open(System::String ^ path, System::IO::FileMode mode);

public static System.IO.FileStream Open (string path, System.IO.FileMode mode);

static member Open : string * System.IO.FileMode -> System.IO.FileStream

Public Shared Function Open (path As String, mode As FileMode) As FileStream

参数

path: String

要打开的文件。

mode: FileMode

FileMode 值，用于指定在文件不存在时是否创建该文件，并确定是保留还是覆盖现有文件的内容。

FileStream

以读/写访问与不共享权限打开的指定模式和路径上的 FileStream。

例外

ArgumentException

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。

DirectoryNotFoundException

指定的路径无效（例如，它位于未映射的驱动器上）。

IOException

打开文件时发生 I/O 错误。

UnauthorizedAccessException

path 指定了一个只读文件。

- 或 -

当前平台不支持此操作。

- 或 -

path 指定了一个目录。

- 或 -

调用方没有所要求的权限。

- 或 -

mode 为 Create，指定文件为隐藏文件。

ArgumentOutOfRangeException

mode 指定了一个无效值。

FileNotFoundException

未找到 path 中指定的文件。

NotSupportedException

path 的格式无效。

示例

下面的代码示例创建一个临时文件，并向其写入一些文本。然后，该示例使用 T：System.IO.FileMode.Open 打开文件;也就是说，如果文件尚不存在，则不会创建该文件。

using namespace System;
using namespace System::IO;
using namespace System::Text;

int main()
{
   // Create a temporary file, and put some data into it.
   String^ path = Path::GetTempFileName();
   FileStream^ fs = File::Open( path, FileMode::Open, FileAccess::Write, FileShare::None );
   try
   {
      array<Byte>^info = (gcnew UTF8Encoding( true ))->GetBytes( "This is some text in the file." );
      
      // Add some information to the file.
      fs->Write( info, 0, info->Length );
   }
   finally
   {
      if ( fs )
            delete (IDisposable^)fs;
   }

   // Open the stream and read it back.
   fs = File::Open( path, FileMode::Open );
   try
   {
      array<Byte>^b = gcnew array<Byte>(1024);
      UTF8Encoding^ temp = gcnew UTF8Encoding( true );
      while ( fs->Read( b, 0, b->Length ) > 0 )
      {
         Console::WriteLine( temp->GetString( b ) );
      }
   }
   finally
   {
      if ( fs )
            delete (IDisposable^)fs;
   }
}

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

class Test
{
    public static void Main()
    {
        // Create a temporary file, and put some data into it.
        string path = Path.GetTempFileName();
        using (FileStream fs = File.Open(path, FileMode.Open, FileAccess.Write, FileShare.None))
        {
            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 = File.Open(path, 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));
            }
        }
    }
}

open System.IO
open System.Text

// Create a temporary file, and put some data into it.
let path = Path.GetTempFileName()

do
    use fs =
        File.Open(path, FileMode.Open, FileAccess.Write, FileShare.None)

    let info =
        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.
do
    use fs = File.Open(path, FileMode.Open)
    let b = Array.zeroCreate 1024
    let temp = UTF8Encoding true

    while fs.Read(b, 0, b.Length) > 0 do
        printfn $"{temp.GetString b}"

Imports System.IO
Imports System.Text

Public Class Test
  Public Shared Sub Main()
  
    ' Create a temporary file, and put some data into it. 
    Dim path1 As String = Path.GetTempFileName()
    Using fs As FileStream = File.Open(path1, FileMode.Open, FileAccess.Write, FileShare.None)
      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)
    End Using

    ' Open the stream and read it back. 
    Using fs As FileStream = File.Open(path1, 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
    End Using

  End Sub
End Class

注解

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

Open(String, FileStreamOptions)

Source:: File.cs

Source:: File.cs

Source:: File.cs

使用指定的路径、创建模式、读/写和共享权限、其他 FileStreams 对同一文件的访问权限、缓冲区大小、其他文件选项和分配大小初始化类的新实例 FileStream 。

public:
 static System::IO::FileStream ^ Open(System::String ^ path, System::IO::FileStreamOptions ^ options);

public static System.IO.FileStream Open (string path, System.IO.FileStreamOptions options);

static member Open : string * System.IO.FileStreamOptions -> System.IO.FileStream

Public Shared Function Open (path As String, options As FileStreamOptions) As FileStream

参数

path: String

要打开的文件的路径。

options: FileStreamOptions

描述要使用的可选 FileStream 参数的对象。

FileStream

包装 FileStream 打开的文件的实例。

注解

FileStream(String, FileStreamOptions) 获取有关异常的信息。

适用于

Open(String, FileMode, FileAccess)

Source:: File.cs

Source:: File.cs

Source:: File.cs

通过指定的模式和不共享的访问权限打开指定路径上的 FileStream。

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

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

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

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

参数

path: String

要打开的文件。

mode: FileMode

FileMode 值，用于指定在文件不存在时是否创建该文件，并确定是保留还是覆盖现有文件的内容。

access: FileAccess

一个 FileAccess 值，它指定可以对文件执行的操作。

FileStream

一个非共享的 FileStream，它提供对指定文件的访问，并且具有指定的模式和访问权限。

例外

ArgumentException

- 或 -

access 指定了 Read，并且 mode 指定了 Create、CreateNew、Truncate 或 Append。

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。

DirectoryNotFoundException

指定的路径无效（例如，它位于未映射的驱动器上）。

IOException

打开文件时发生 I/O 错误。

UnauthorizedAccessException

path 指定了一个只读文件，并且 access 不是 Read。

- 或 -

path 指定了一个目录。

- 或 -

调用方没有所要求的权限。

- 或 -

mode 为 Create，指定文件为隐藏文件。

ArgumentOutOfRangeException

mode 或 access 指定了一个无效值。

FileNotFoundException

未找到 path 中指定的文件。

NotSupportedException

path 的格式无效。

示例

以下示例打开具有只读访问权限的文件。


using namespace System;
using namespace System::IO;
using namespace System::Text;

int main()
{
    // This sample assumes that you have a folder named "c:\temp" on your computer.
    String^ filePath = "c:\\temp\\MyTest.txt";
    // Delete the file if it exists.
    if (File::Exists( filePath ))
    {
        File::Delete( filePath );
    }
    // Create the file.
    FileStream^ fs = File::Create( filePath );
    try
    {
        array<Byte>^ info = ( gcnew UTF8Encoding( true ))->GetBytes( "This is some text in the file." );
        
        // Add some information to the file.
        fs->Write( info, 0, info->Length );
    }
    finally
    {
        if ( fs )
            delete (IDisposable^)fs;
    }

    // Open the stream and read it back.
    fs = File::Open( filePath, FileMode::Open, FileAccess::Read );
    try
    {
        array<Byte>^ b = gcnew array<Byte>(1024);
        UTF8Encoding^ temp = gcnew 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() );
        }
    }
    finally
    {
        if ( fs )
            delete (IDisposable^)fs;
    }
}

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

class Test
{
    public static void Main()
    {
        // This sample assumes that you have a folder named "c:\temp" on your computer.
        string filePath = @"c:\temp\MyTest.txt";

        // Delete the file if it exists.
        if (File.Exists(filePath))
        {
            File.Delete(filePath);
        }

        // Create the file.
        using (FileStream fs = File.Create(filePath))
        {
            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 = File.Open(filePath, 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());
            }
        }
    }
}

open System.IO
open System.Text

// This sample assumes that you have a folder named "c:\temp" on your computer.
let filePath = @"c:\temp\MyTest.txt"

// Delete the file if it exists.
if File.Exists filePath then
    File.Delete filePath

// Create the file.
do
    use fs = File.Create filePath

    let info =
        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.
do
    use fs =
        File.Open(filePath, FileMode.Open, FileAccess.Read)

    let b = Array.zeroCreate 1024
    let temp = UTF8Encoding true

    while fs.Read(b, 0, b.Length) > 0 do
        printfn $"{temp.GetString b}"

    try
        // Try to write to the file.
        fs.Write(b, 0, b.Length)
    with
    | e -> printfn $"Writing was disallowed, as expected: {e}"

Imports System.IO
Imports System.Text

Public Class Test
  Public Shared Sub Main()
    ' This sample assumes that you have a folder named "c:\temp" on your computer. 
    Dim filePath As String = "c:\temp\MyTest.txt"

    ' Delete the file if it exists. 
    If File.Exists(filePath) Then
      File.Delete(filePath)
    End If

    ' Create the file.
    Using fs As FileStream = File.Create(filePath)
      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)
    End Using

    ' Open the stream and read it back.
    Using fs As FileStream = File.Open(filePath, FileMode.Open, FileAccess.Read)
      Dim b(1023) As Byte
      Dim temp As UTF8Encoding = New UTF8Encoding(True)

      ' Display the information on the console. 
      Do While fs.Read(b, 0, b.Length) > 0
        Console.WriteLine(temp.GetString(b))
      Loop

      Try
        ' Try to write to the file
        fs.Write(b, 0, b.Length)
      Catch e As Exception
        Console.WriteLine("Writing was disallowed, as expected: " & e.ToString())
      End Try

    End Using

  End Sub
End Class

注解

允许 path 参数指定相对或绝对路径信息。相对路径信息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。

另请参阅

适用于

File.Open 方法

定义

重载

Open(String, FileMode, FileAccess, FileShare)

参数

返回

例外

示例

注解

另请参阅

适用于

Open(String, FileMode)

参数

返回

例外

示例

注解

另请参阅

适用于

Open(String, FileStreamOptions)

参数

返回

注解

适用于

Open(String, FileMode, FileAccess)

参数

返回

例外

示例

注解

另请参阅

适用于

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