FileStream.CanRead FileStream.CanRead FileStream.CanRead FileStream.CanRead Property

定义

获取一个值,该值指示当前流是否支持读取。Gets a value that indicates whether the current stream supports reading.

public:
 virtual property bool CanRead { bool get(); };
public override bool CanRead { get; }
member this.CanRead : bool
Public Overrides ReadOnly Property CanRead As 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 falsetrue if the stream supports reading; false if the stream is closed or was opened with write-only access.

示例

下面的示例演示CanRead属性的用法。The following example demonstrates a use of the CanRead property. 此代码的输出为 "Myfile.txt 不可写。"The output of this code is "MyFile.txt is not writable." 若要获取输出消息 "myfile.txt 可以写入和读取。",请在FileAccess FileStream构造函数中将参数更改为ReadWriteTo get the output message "MyFile.txt can be both written to and read from.", change the FileAccess parameter to ReadWrite in the FileStream constructor.

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;
}

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.");
        }
    }
}
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

注解

如果Stream从派生的类不支持读取,则对、 ReadByteRead BeginRead方法的调用将引发NotSupportedExceptionIf a class derived from Stream does not support reading, calls to the Read, ReadByte, and BeginRead methods throw a NotSupportedException.

如果流已关闭, 则此属性返回falseIf the stream is closed, this property returns false.

适用于

另请参阅