FileStream.CanRead 属性

  • 参考

定义

命名空间:
System.IO
程序集:
mscorlib.dll, System.IO.FileSystem.dll
程序集:
System.Runtime.dll
程序集:
System.IO.FileSystem.dll
程序集:
mscorlib.dll
程序集:
netstandard.dll
Source:
FileStream.cs
Source:
FileStream.cs
Source:
FileStream.cs

获取一个值，该值指示当前流是否支持读取。

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

Boolean

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。

示例

下面的示例演示如何使用 CanRead 属性。 此代码的输出为“MyFile.txt 不可写”。若要获取输出消息“MyFile.txt 可以写入和读取”。，请将 构造函数中的 FileStream 参数更改为 。FileAccessReadWrite

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.");
        }
    }
}

open System.IO

let fs = new FileStream("MyFile.txt", FileMode.OpenOrCreate, FileAccess.Read)

if fs.CanRead && fs.CanWrite then
    printfn "MyFile.txt can be both written to and read from."
else if fs.CanRead then
    printfn "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 、 ReadByte和 BeginRead 方法的Read调用会引发 NotSupportedException。

如果流关闭，此属性返回 false。

适用于

另请参阅