FileStream.CanWrite 屬性
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
取得值,表示目前資料流是否支援寫入。
public:
virtual property bool CanWrite { bool get(); };
public override bool CanWrite { get; }
member this.CanWrite : bool
Public Overrides ReadOnly Property CanWrite As Boolean
如果資料流支援寫入,則為 true
;如果資料流已關閉或以唯讀存取開啟,則為 false
。
下列範例會 CanWrite
使用 屬性來檢查數據流是否支援寫入。
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
以下是使用 屬性的 CanWrite
範例。 此程式代碼的輸出為「MyFile.txt 可寫入」。若要取得輸出訊息「MyFile.txt 可以同時寫入和讀取。」,請將 FileAccess
建構函式中的 FileStream
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::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
如果衍生自 Stream 類別不支援寫入,呼叫SetLength、 Write或 BeginWriteWriteByte 會NotSupportedException擲回 。
如果資料流已關閉,這個屬性會傳 false
回 。
產品 | 版本 |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.3, 1.4, 1.6, 2.0, 2.1 |
UWP | 10.0 |