WaitOrTimerCallback 代理人

定義

命名空間:

System.Threading

組件:

netstandard.dll, System.Threading.ThreadPool.dll

來源:

ThreadPoolWorkQueue.cs

表示 WaitHandle 收到信號或逾時時呼叫的方法。

public delegate void WaitOrTimerCallback(System::Object ^ state, bool timedOut);

public delegate void WaitOrTimerCallback(object? state, bool timedOut);

type WaitOrTimerCallback = delegate of obj * bool -> unit

Public Delegate Sub WaitOrTimerCallback(state As Object, timedOut As Boolean)

參數

state

Object

物件，它包含回呼方法所使用的資訊。

timedOut

Boolean

true，表示 WaitHandle 逾時；false，表示收到信號。

範例

下列範例示範如何使用 WaitOrTimerCallback 委派來表示在發出等候控制碼時所執行的回呼方法。

此範例也會示範如何在發出指定的等候控制碼時，使用 RegisterWaitForSingleObject 方法來執行指定的回呼方法。 在此範例中，回呼方法是 WaitProc ，而等候控制碼是 AutoResetEvent 。

此範例會定義類別 TaskInfo ，以保存在執行時傳遞至回呼的資訊。 此範例會 TaskInfo 建立 物件，並指派一些字串資料。 方法傳 RegisterWaitForSingleObject 回的 TaskInfo 會指派給 Handle 物件的欄位，讓回呼方法可以存取 RegisteredWaitHandle 。 RegisteredWaitHandle

除了 TaskInfo 物件之外，呼叫 RegisterWaitForSingleObject 方法還會指定 AutoResetEvent 工作等候的時間、代表 WaitProc 回呼方法的委派、 WaitOrTimerCallback 一秒的逾時間隔和多個回呼。

當主執行緒藉由呼叫 其 Set 方法發出訊 AutoResetEvent 號時， WaitOrTimerCallback 會叫用委派。 方法 WaitProc 會測試 RegisteredWaitHandle 以判斷是否發生逾時。 如果因為已發出等候控制碼而叫用回呼，則方法會取消註冊 RegisteredWaitHandle ， WaitProc 並停止進一步的回呼。 在逾時的情況下，工作會繼續等候。 方法會 WaitProc 以將訊息列印至主控台結束。

using System;
using System.Threading;

// TaskInfo contains data that will be passed to the callback
// method.
public class TaskInfo {
    public RegisteredWaitHandle Handle = null;
    public string OtherInfo = "default";
}

public class Example {
    public static void Main(string[] args) {
        // The main thread uses AutoResetEvent to signal the
        // registered wait handle, which executes the callback
        // method.
        AutoResetEvent ev = new AutoResetEvent(false);

        TaskInfo ti = new TaskInfo();
        ti.OtherInfo = "First task";
        // The TaskInfo for the task includes the registered wait
        // handle returned by RegisterWaitForSingleObject.  This
        // allows the wait to be terminated when the object has
        // been signaled once (see WaitProc).
        ti.Handle = ThreadPool.RegisterWaitForSingleObject(
            ev,
            new WaitOrTimerCallback(WaitProc),
            ti,
            1000,
            false
        );

        // The main thread waits three seconds, to demonstrate the
        // time-outs on the queued thread, and then signals.
        Thread.Sleep(3100);
        Console.WriteLine("Main thread signals.");
        ev.Set();

        // The main thread sleeps, which should give the callback
        // method time to execute.  If you comment out this line, the
        // program usually ends before the ThreadPool thread can execute.
        Thread.Sleep(1000);
        // If you start a thread yourself, you can wait for it to end
        // by calling Thread.Join.  This option is not available with 
        // thread pool threads.
    }
   
    // The callback method executes when the registered wait times out,
    // or when the WaitHandle (in this case AutoResetEvent) is signaled.
    // WaitProc unregisters the WaitHandle the first time the event is 
    // signaled.
    public static void WaitProc(object state, bool timedOut) {
        // The state object must be cast to the correct type, because the
        // signature of the WaitOrTimerCallback delegate specifies type
        // Object.
        TaskInfo ti = (TaskInfo) state;

        string cause = "TIMED OUT";
        if (!timedOut) {
            cause = "SIGNALED";
            // If the callback method executes because the WaitHandle is
            // signaled, stop future execution of the callback method
            // by unregistering the WaitHandle.
            if (ti.Handle != null)
                ti.Handle.Unregister(null);
        } 

        Console.WriteLine("WaitProc( {0} ) executes on thread {1}; cause = {2}.",
            ti.OtherInfo, 
            Thread.CurrentThread.GetHashCode().ToString(), 
            cause
        );
    }
}

Imports System.Threading

' TaskInfo contains data that will be passed to the callback
' method.
Public Class TaskInfo
    public Handle As RegisteredWaitHandle = Nothing
    public OtherInfo As String = "default"
End Class

Public Class Example

    <MTAThread> _
    Public Shared Sub Main()
        ' The main thread uses AutoResetEvent to signal the
        ' registered wait handle, which executes the callback
        ' method.
        Dim ev As New AutoResetEvent(false)

        Dim ti As New TaskInfo()
        ti.OtherInfo = "First task"
        ' The TaskInfo for the task includes the registered wait
        ' handle returned by RegisterWaitForSingleObject.  This
        ' allows the wait to be terminated when the object has
        ' been signaled once (see WaitProc).
        ti.Handle = ThreadPool.RegisterWaitForSingleObject( _
            ev, _
            New WaitOrTimerCallback(AddressOf WaitProc), _
            ti, _
            1000, _
            false _
        )

        ' The main thread waits about three seconds, to demonstrate 
        ' the time-outs on the queued task, and then signals.
        Thread.Sleep(3100)
        Console.WriteLine("Main thread signals.")
        ev.Set()

        ' The main thread sleeps, which should give the callback
        ' method time to execute.  If you comment out this line, the
        ' program usually ends before the ThreadPool thread can execute.
        Thread.Sleep(1000)
        ' If you start a thread yourself, you can wait for it to end
        ' by calling Thread.Join.  This option is not available with 
        ' thread pool threads.
    End Sub
   
    ' The callback method executes when the registered wait times out,
    ' or when the WaitHandle (in this case AutoResetEvent) is signaled.
    ' WaitProc unregisters the WaitHandle the first time the event is 
    ' signaled.
    Public Shared Sub WaitProc(state As Object, timedOut As Boolean)
        ' The state object must be cast to the correct type, because the
        ' signature of the WaitOrTimerCallback delegate specifies type
        ' Object.
        Dim ti As TaskInfo = CType(state, TaskInfo)

        Dim cause As String = "TIMED OUT"
        If Not timedOut Then
            cause = "SIGNALED"
            ' If the callback method executes because the WaitHandle is
            ' signaled, stop future execution of the callback method
            ' by unregistering the WaitHandle.
            If Not ti.Handle Is Nothing Then
                ti.Handle.Unregister(Nothing)
            End If
        End If 

        Console.WriteLine("WaitProc( {0} ) executes on thread {1}; cause = {2}.", _
            ti.OtherInfo, _
            Thread.CurrentThread.GetHashCode().ToString(), _
            cause _
        )
    End Sub
End Class

備註

WaitOrTimerCallback 表示當已註冊的等候控制碼逾時或發出訊號時，所要執行的回呼方法。 將回呼方法傳遞至 WaitOrTimerCallback 建構函式，以建立委派。 您的方法必須有此處顯示的簽章。

將委派和 WaitHandle 傳遞 WaitOrTimerCallback 至 ThreadPool.RegisterWaitForSingleObject ，以建立已註冊的等候控制碼。 每次逾時或發出訊號時， WaitHandle 您的回呼方法都會執行。

注意

Visual Basic 使用者可以省略建 WaitOrTimerCallback 構函式，只要在將回呼方法傳遞至 RegisterWaitForSingleObject 時使用 AddressOf 運算子即可。 Visual Basic 會自動呼叫正確的委派建構函式。

如果您想要將資訊傳遞至回呼方法，請建立包含必要資訊的物件，並在建立已註冊的等候控制碼時傳遞至 RegisterWaitForSingleObject 。 每次回呼方法執行時， state 參數都會包含這個物件。

如需使用回呼方法來同步處理執行緒集區執行緒的詳細資訊，請參閱 受控執行緒集區。

擴充方法

名稱	Description
GetMethodInfo(Delegate)	取得表示特定委派所代表之方法的物件。

另請參閱

• 執行緒和執行緒處理
• 受控執行緒集區