FileStream.CanRead 属性

项目
08/17/2007

获取一个值，该值指示当前流是否支持读取。

**命名空间:**System.IO
**程序集:**mscorlib（在 mscorlib.dll 中）

语法

声明
Public Overrides ReadOnly Property CanRead As Boolean
用法
Dim instance As FileStream
Dim value As Boolean

value = instance.CanRead

public override bool CanRead { get; }

public:
virtual property bool CanRead {
    bool get () override;
}

/** @property */
public boolean get_CanRead ()

public override function get CanRead () : boolean

属性值

如果流支持读取，则为 true；如果流已关闭或是通过只写访问方式打开的，则为 false。

备注

如果从 Stream 派生的类不支持读取，则调用 Read、ReadByte 和 BeginRead 方法将引发 NotSupportedException。

如果该流已关闭，此属性将返回 false。

示例

下面的示例演示了 CanRead 属性的用法。此代码的输出是“MyFile.txt is not writable.”。若要获取输出消息“MyFile.txt can be both written to and read from.”，请将 FileStream 构造函数中的 FileAccess 参数更改为 ReadWrite。

Imports System
Imports System.IO

Class TestRW

    Public Shared Sub Main()
        Dim fs As New FileStream("MyFile.txt", FileMode.OpenOrCreate, FileAccess.Read)
        If fs.CanRead And fs.CanWrite Then
            Console.WriteLine("MyFile.txt can be both written to and read from.")
        Else
            If fs.CanRead Then
                Console.WriteLine("MyFile.txt is not writable.")
            End If
        End If
    End Sub
End Class

using System;
using System.IO;
 
class TestRW 
{
    public static void Main(String[] args)
    {
        FileStream fs = new FileStream("MyFile.txt", FileMode.OpenOrCreate, FileAccess.Read);
        if (fs.CanRead && fs.CanWrite)
        {
            Console.WriteLine("MyFile.txt can be both written to and read from.");
        }
        else if (fs.CanRead)
        {
            Console.WriteLine("MyFile.txt is not writable.");
        }
    }
}

using namespace System;
using namespace System::IO;
int main( void )
{
   FileStream^ fs = gcnew FileStream( "MyFile.txt",FileMode::OpenOrCreate,FileAccess::Read );
   if ( fs->CanRead && fs->CanWrite )
   {
      Console::WriteLine( "MyFile.txt can be both written to and read from." );
   }
   else
   {
      Console::WriteLine( "MyFile.txt is not writable" );
   }

   return 0;
}

import System.*;
import System.IO.*;

class TestRW
{
    public static void main(String[] args)
    {
        FileStream fs = new FileStream("MyFile.txt", 
            FileMode.OpenOrCreate, FileAccess.Read);
        if (fs.get_CanRead() && fs.get_CanWrite()) {
            Console.WriteLine("MyFile.txt can be both written to " 
                + "and read from.");
        }
        else {
            if (fs.get_CanRead()) {
                Console.WriteLine("MyFile.txt is not writable.");
            }
        }
    } //main
} //TestRW

 import System;
 import System.IO;
 
class TestRW 
{
   public static function Main() : void 
   {
 
         var fs : FileStream = new FileStream("MyFile.txt", FileMode.OpenOrCreate, FileAccess.Read);
         if (fs.CanRead && fs.CanWrite)
         {
            Console.WriteLine("MyFile.txt can be both written to and read from.");
         }
         else if (fs.CanRead)
         {
            Console.WriteLine("MyFile.txt is not writable.");
      }
   }
}
TestRW.Main();

平台

Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition

.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。

通过

FileStream.CanRead 属性

语法

属性值

备注

示例

平台

版本信息

.NET Framework

.NET Compact Framework

请参见

参考

其他资源

其他资源