Stream.CanRead 属性

定义

命名空间:

System.IO

程序集:

System.Runtime.dll

Source:

Stream.cs

当在派生类中重写时，获取指示当前流是否支持读取的值。

public:
 abstract property bool CanRead { bool get(); };

public abstract bool CanRead { get; }

member this.CanRead : bool

Public MustOverride ReadOnly Property CanRead As Boolean

属性值

Boolean

如果流支持读取，为 true；否则为 false。

示例

下面是使用 CanRead 属性的示例。

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

如果派生自 Stream 的类不支持读取，则对 Read、 ReadByte和 BeginRead 方法的调用将引发 NotSupportedException。

另请参阅

• 文件和流 I/O
• 如何：从文件中读取文本
• 如何：将文本写入文件