FileStream.CanWrite Eigenschaft

Definition

Namespace:

System.IO

Assembly:

System.Runtime.dll

Source:

FileStream.cs

Ruft einen Wert ab, der angibt, ob der aktuelle Stream Schreibvorgänge unterstützt.

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

public override bool CanWrite { get; }

member this.CanWrite : bool

Public Overrides ReadOnly Property CanWrite As Boolean

Eigenschaftswert

Boolean

true, wenn der Stream Schreibvorgänge unterstützt, false, wenn der Stream geschlossen ist oder mit schreibgeschütztem Zugriff geöffnet wurde.

Beispiele

Im folgenden Beispiel wird die CanWrite -Eigenschaft verwendet, um zu überprüfen, ob ein Stream das Schreiben unterstützt.

using namespace System;
using namespace System::IO;
using namespace System::Text;

int main()
{
   String^ path = "c:\\temp\\MyTest.txt";
   
   // Ensure that the file is readonly.
   File::SetAttributes( path, static_cast<FileAttributes>(File::GetAttributes( path ) | FileAttributes::ReadOnly) );
   
   //Create the file.
   FileStream^ fs = gcnew FileStream( path,FileMode::OpenOrCreate,FileAccess::Read );
   try
   {
      if ( fs->CanWrite )
      {
         Console::WriteLine( "The stream for file {0} is writable.", path );
      }
      else
      {
         Console::WriteLine( "The stream for file {0} is not writable.", path );
      }
   }
   finally
   {
      if ( fs )
         delete (IDisposable^)fs;
   }
}

using System;
using System.IO;
using System.Text;

class Test
{
    
    public static void Main()
    {
        string path = @"c:\temp\MyTest.txt";

        // Ensure that the file is readonly.
        File.SetAttributes(path, File.GetAttributes(path) | FileAttributes.ReadOnly);

        //Create the file.
        using (FileStream fs = new FileStream (path, FileMode.OpenOrCreate, FileAccess.Read))
        {
            if (fs.CanWrite)
            {
                Console.WriteLine("The stream for file {0} is writable.", path);
            }
            else
            {
                Console.WriteLine("The stream for file {0} is not writable.", path);
            }
        }
    }
}

open System.IO

let path = @"c:\temp\MyTest.txt"

// Ensure that the file is readonly.
File.SetAttributes(path, File.GetAttributes path ||| FileAttributes.ReadOnly)

//Create the file.
do
    use fs = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Read)

    if fs.CanWrite then
        printfn $"The stream for file {path} is writable."

    else
        printfn $"The stream for file {path} is not writable."

Imports System.IO

Public Class Test

    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"

        'Ensure that the file is readonly.
        File.SetAttributes(path, File.GetAttributes(path) Or FileAttributes.ReadOnly)

        'Create the file.
        Dim fs As FileStream = New FileStream(path, FileMode.OpenOrCreate, FileAccess.Read)

        If fs.CanWrite Then
            Console.WriteLine("The stream connected to {0} is writable.", path)
        Else
            Console.WriteLine("The stream connected to {0} is not writable.", path)
        End If
        fs.Close()
    End Sub
End Class

Im folgenden Beispiel wird die CanWrite -Eigenschaft verwendet. Die Ausgabe dieses Codes lautet "MyFile.txt beschreibbar ist". Um die Ausgabemeldung "MyFile.txt kann sowohl in als auch aus gelesen werden" abzurufen, ändern Sie den FileAccess Parameter im FileStream Konstruktor inReadWrite.

using namespace System;
using namespace System::IO;
int main( void )
{
   FileStream^ fs = gcnew FileStream( "MyFile.txt",FileMode::OpenOrCreate,FileAccess::Write );
   if ( fs->CanRead && fs->CanWrite )
   {
      Console::WriteLine( "MyFile.txt can be both written to and read from." );
   }
   else
   {
      Console::WriteLine( "MyFile.txt is 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.Write);
        if (fs.CanRead && fs.CanWrite)
        {
            Console.WriteLine("MyFile.txt can be both written to and read from.");
        }
        else if (fs.CanWrite)
        {
            Console.WriteLine("MyFile.txt is writable.");
        }
    }
}

open System.IO

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

if fs.CanRead && fs.CanWrite then
    printfn "MyFile.txt can be both written to and read from."
elif fs.CanWrite then
    printfn "MyFile.txt is writable."

Imports System.IO

Class TestRW
    Public Shared Sub Main()
        Dim fs As New FileStream("MyFile.txt", FileMode.OpenOrCreate, FileAccess.Write)

        If fs.CanRead And fs.CanWrite Then
            Console.WriteLine("MyFile.txt can be both written to and read from.")
        ElseIf fs.CanWrite Then
            Console.WriteLine("MyFile.txt is writable.")
        End If
    End Sub
End Class

Hinweise

Wenn eine von Stream abgeleitete Klasse das Schreiben nicht unterstützt, löst ein Aufruf von SetLength, Write, BeginWriteoder WriteByte einen aus NotSupportedException.

Wenn der Stream geschlossen ist, gibt diese Eigenschaft zurück false.

Weitere Informationen

• Datei- und Stream-E/A
• How to: Lesen von Text aus einer Datei
• How to: Schreiben von Text in eine Datei