FileStream.IsAsync 屬性

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

public virtual bool IsAsync { get; }

member this.IsAsync : bool

Public Overridable ReadOnly Property IsAsync As Boolean

屬性值

true如果在 Windows 上為重疊 I/O 開啟了這個柄。 在 Unix 上，true如果串流在 .NET 10 及更早版本中開啟非同步 I/O，或檔案描述符在 .NET 11 及以後版本設定O_NONBLOCK了標誌;否則， false

範例

此程式碼範例是建構子更大範例 FileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean) 的一部分。

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

備註

這個 IsAsync 屬性會顯示該 FileStream 句柄是否被設定為非同步 I/O，讓你的程式碼能正確使用這個 Handle 屬性。 在 Win32 中， IsAsync 為真表示 handle 是為了重疊 I/O而開啟，因此需要不同的參數 和 ReadFileWriteFile。 在 Unix 上，從 .NET 11 開始，會反映檔案描述符是否設定了O_NONBLOCK該標誌。

當您使用具有FileStream、 isAsync或 useAsync 參數的建構函式來建立 類別的options實例時，您可以指定此值。 該屬性不必是 ， true 才能呼叫 ReadAsync、 WriteAsync或 CopyToAsync 方法。 當屬性是 且 false 你呼叫非同步讀寫方法時，UI 執行緒不會被阻塞，但輸入輸出是同步執行的。

另請參閱

• 檔案和數據流 I/O
• 如何：從檔案讀取文字
• 如何：將文字寫入檔案