FileStream.CanRead 屬性

定義

命名空間:

System.IO

組件:

System.Runtime.dll

來源:

FileStream.cs

取得值，表示目前資料流是否支援讀取。

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

public override bool CanRead { get; }

member this.CanRead : bool

Public Overrides ReadOnly Property CanRead As Boolean

屬性值

Boolean

如果資料流支援讀取，則為 true；如果資料流已關閉或以唯寫存取開啟，則為 false。

範例

下列範例示範 屬性的使用 CanRead 。 此程式代碼的輸出為「無法寫入 MyFile.txt」。若要取得輸出訊息「MyFile.txt 可以寫入和讀取。」，請在建構函式中FileStream將 FileAccess 參數變更為 ReadWrite 。

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

備註

如果衍生自 Stream 的類別不支援讀取， 則呼叫、 ReadByte和 BeginRead 方法會Read擲回 NotSupportedException。

如果資料流已關閉，這個屬性會傳 false回 。

另請參閱

• 檔案和資料流 I/O
• 作法：讀取檔案中的文字
• 作法：將文字寫入檔案