FileStream.IsAsync Properti

Definisi

Ruang nama:

System.IO

Rakitan:

System.Runtime.dll

Sumber:

FileStream.cs

Mendapatkan nilai yang menunjukkan apakah FileStream dibuka secara asinkron atau sinkron.

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

public virtual bool IsAsync { get; }

member this.IsAsync : bool

Public Overridable ReadOnly Property IsAsync As Boolean

Nilai Properti

Boolean

trueFileStream jika dibuka secara asinkron; jika tidak, false.

Contoh

Contoh kode ini adalah bagian dari contoh yang lebih besar yang disediakan untuk FileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean) konstruktor.

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);
}

// Create a synchronization object that gets
// signaled when verification is complete.
let manualEvent = new ManualResetEvent false

// Create random data to write to the file.
let writeArray = Array.zeroCreate 100000
Random.Shared.NextBytes writeArray

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

// Check that the FileStream was opened asynchronously.

if fStream.IsAsync then "" else "not "
|> printfn "fStream was %sopened asynchronously."

// Asynchronously write to the file.
let asyncResult =
    fStream.BeginWrite(
        writeArray,
        0,
        writeArray.Length,
        AsyncCallback endWriteCallback,
        State(fStream, writeArray, manualEvent)
    )

// Concurrently do other work and then wait
// for the data to be written and verified.
manualEvent.WaitOne(5000, false) |> ignore

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

Keterangan

Properti IsAsync mendeteksi apakah FileStream handel dibuka secara asinkron, memungkinkan kode Anda untuk menggunakan Handle properti dengan benar. Di Win32, IsAsync menjadi benar berarti handel dibuka untuk I/O yang tumpang tindih, dan dengan demikian memerlukan parameter yang berbeda ke ReadFile dan WriteFile.

Anda menentukan nilai ini saat membuat instans FileStream kelas menggunakan konstruktor yang memiliki isAsyncparameter , useAsync, atau options . Ketika properti adalah true, aliran menggunakan I/O yang tumpang tindih untuk melakukan operasi file secara asinkron. Namun, IsAsync properti tidak harus true memanggil ReadAsyncmetode , WriteAsync, atau CopyToAsync . IsAsync Ketika properti adalah false dan Anda memanggil operasi baca dan tulis asinkron, utas UI masih belum diblokir, tetapi operasi I/O aktual dilakukan secara sinkron.

Lihat juga

• I/O File dan Aliran
• Cara: Membaca Teks dari File
• Cara: Menulis Teks ke File