File.OpenRead(String) 方法

定义

打开现有文件以进行读取。

public:
 static System::IO::FileStream ^ OpenRead(System::String ^ path);
public static System.IO.FileStream OpenRead (string path);
static member OpenRead : string -> System.IO.FileStream
Public Shared Function OpenRead (path As String) As FileStream

参数

path
String

要打开以进行读取的文件。

返回

FileStream

指定路径上的只读 FileStream

例外

.NET Framework 2.1 以前的 .NET Core 版本:是长度为零的字符串,仅包含空格,或包含一 path 个或多个无效字符。 你可以使用 GetInvalidPathChars() 方法查询无效字符。

pathnull

指定的路径和/或文件名超过了系统定义的最大长度。

指定的路径无效(例如,它位于未映射的驱动器上)。

path 指定了一个目录。

  • 或 - 调用方没有所要求的权限。

未找到 path 中指定的文件。

path 的格式无效。

打开文件时发生 I/O 错误。

示例

以下示例将打开一个要读取的文件。

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

int main()
{
   String^ path = "c:\\temp\\MyTest.txt";
   
   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::OpenRead( path );
   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()
    {
        string path = @"c:\temp\MyTest.txt";

        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.OpenRead(path))
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);

            while (fs.Read(b,0,b.Length) > 0)
            {
                Console.WriteLine(temp.GetString(b));
            }
        }
    }
}
Imports System.IO
Imports System.Text

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

    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.OpenRead(path)
      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

此方法等效于值为 、值为 且 FileStream(String, FileMode, FileAccess, FileShare) FileMode 值为 Open FileAccess ReadFileShare 构造函数重载 Read

path允许 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

有关常见 I/O 任务的列表,请参阅 常见 I/O 任务

适用于

另请参阅