FileStream.IsAsync FileStream.IsAsync FileStream.IsAsync FileStream.IsAsync Property

定義

FileStream が非同期的に開かれたか、同期的に開かれたかを示す値を取得します。Gets a value that indicates whether the FileStream was opened asynchronously or synchronously.

public:
 virtual property bool IsAsync { bool get(); };
public virtual bool IsAsync { get; }
member this.IsAsync : bool
Public Overridable ReadOnly Property IsAsync As Boolean

プロパティ値

FileStream が非同期的に開かれた場合は true。それ以外の場合は falsetrue if the FileStream was opened asynchronously; otherwise, false.

このコード例は、 FileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean)コンストラクターに対して提供されるより大きな例の一部です。This code example is part of a larger example provided for the FileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean) constructor.

int main()
{
   
   // Create a synchronization object that gets 
   // signaled when verification is complete.
   ManualResetEvent^ manualEvent = gcnew ManualResetEvent( false );
   
   // Create the data to write to the file.
   array<Byte>^writeArray = gcnew array<Byte>(100000);
   (gcnew Random)->NextBytes( writeArray );
   FileStream^ fStream = gcnew FileStream(  "Test#@@#.dat",FileMode::Create,FileAccess::ReadWrite,FileShare::None,4096,true );
   
   // Check that the FileStream was opened asynchronously.
   Console::WriteLine( "fStream was {0}opened asynchronously.", fStream->IsAsync ? (String^)"" : "not " );
   
   // Asynchronously write to the file.
   IAsyncResult^ asyncResult = fStream->BeginWrite( writeArray, 0, writeArray->Length, gcnew AsyncCallback( &FStream::EndWriteCallback ), gcnew State( fStream,writeArray,manualEvent ) );
   
   // Concurrently do other work and then wait 
   // for the data to be written and verified.
   manualEvent->WaitOne( 5000, false );
}

static void Main()
{
    // Create a synchronization object that gets 
    // signaled when verification is complete.
    ManualResetEvent manualEvent = new ManualResetEvent(false);

    // Create random data to write to the file.
    byte[] writeArray = new byte[100000];
    new Random().NextBytes(writeArray);

    FileStream fStream = 
        new FileStream("Test#@@#.dat", FileMode.Create, 
        FileAccess.ReadWrite, FileShare.None, 4096, true);

    // Check that the FileStream was opened asynchronously.
    Console.WriteLine("fStream was {0}opened asynchronously.",
        fStream.IsAsync ? "" : "not ");

    // Asynchronously write to the file.
    IAsyncResult asyncResult = fStream.BeginWrite(
        writeArray, 0, writeArray.Length, 
        new AsyncCallback(EndWriteCallback), 
        new State(fStream, writeArray, manualEvent));

    // Concurrently do other work and then wait 
    // for the data to be written and verified.
    manualEvent.WaitOne(5000, false);
}
Shared Sub Main()

    ' Create a synchronization object that gets 
    ' signaled when verification is complete.
    Dim manualEvent As New ManualResetEvent(False)

    ' Create random data to write to the file.
    Dim writeArray(100000) As Byte
    Dim randomGenerator As New Random()
    randomGenerator.NextBytes(writeArray)

    Dim fStream As New FileStream("Test#@@#.dat", _
        FileMode.Create, FileAccess.ReadWrite, _
        FileShare.None, 4096, True)

    ' Check that the FileStream was opened asynchronously.
    If fStream.IsAsync = True
        Console.WriteLine("fStream was opened asynchronously.")
    Else
        Console.WriteLine("fStream was not opened asynchronously.")
    End If

    ' Asynchronously write to the file.
    Dim asyncResult As IAsyncResult = fStream.BeginWrite( _
        writeArray, 0, writeArray.Length, _
        AddressOf EndWriteCallback , _
        New State(fStream, writeArray, manualEvent))

    ' Concurrently do other work and then wait
    ' for the data to be written and verified.
    manualEvent.WaitOne(5000, False)
End Sub

注釈

プロパティIsAsyncは、 FileStreamハンドルが非同期的に開かれたかどうかを検出Handleし、コードがプロパティを正しく使用できるようにします。The IsAsync property detects whether the FileStream handle was opened asynchronously, enabling your code to use the Handle property correctly. Win32 ではIsAsync 、true の場合、ハンドルが重複 i/o 用に開かれていることを意味しReadFileますWriteFile。したがって、とには異なるパラメーターが必要です。In Win32, IsAsync being true means the handle was opened for overlapped I/O, and thus requires different parameters to ReadFile and WriteFile.

このFileStream値はisAsync、、 useAsync、またはoptionsパラメーターを持つコンストラクターを使用して、クラスのインスタンスを作成するときに指定します。You specify this value when you create an instance of the FileStream class using a constructor that has an isAsync, useAsync, or options parameter. プロパティがtrueの場合、ストリームは重複 i/o を利用してファイル操作を非同期に実行します。When the property is true, the stream utilizes overlapped I/O to perform file operations asynchronously. ReadAsync true CopyToAsyncただし、 IsAsyncプロパティは、WriteAsyncメソッド、メソッド、またはメソッドを呼び出す必要はありません。However, the IsAsync property does not have to be true to call the ReadAsync, WriteAsync, or CopyToAsync method. IsAsyncプロパティがfalseで、非同期の読み取り操作と書き込み操作を呼び出すと、UI スレッドはブロックされませんが、実際の i/o 操作は同期的に実行されます。When the IsAsync property is false and you call the asynchronous read and write operations, the UI thread is still not blocked, but the actual I/O operation is performed synchronously.

適用対象

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