RegisteredWaitHandle.Unregister(WaitHandle) 方法
定义
重要
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public:
bool Unregister(System::Threading::WaitHandle ^ waitObject);public bool Unregister (System.Threading.WaitHandle? waitObject);public bool Unregister (System.Threading.WaitHandle waitObject);[System.Runtime.InteropServices.ComVisible(true)]
public bool Unregister (System.Threading.WaitHandle waitObject);member this.Unregister : System.Threading.WaitHandle -> bool[<System.Runtime.InteropServices.ComVisible(true)>]
member this.Unregister : System.Threading.WaitHandle -> boolPublic Function Unregister (waitObject As WaitHandle) As Boolean参数
- waitObject
- WaitHandle
要发出信号的 WaitHandle。
返回
如果函数成功，则为 true；否则为 false。
- 属性
示例
下面的示例演示如何使用 Unregister 此方法在出现回调时取消注册任务，因为已发出等待句柄信号。
该示例还演示如何在发出指定的等待句柄信号时使用 RegisterWaitForSingleObject 该方法执行指定的回调方法。 在此示例中，回调方法是 WaitProc，等待句柄是一个 AutoResetEvent。
该示例定义一个 TaskInfo 类，用于保存在执行回调时传递给回调的信息。 该示例创建一个 TaskInfo 对象并为其分配一些字符串数据。 RegisteredWaitHandle该方法返回RegisterWaitForSingleObject的函数将分配给Handle对象的字段TaskInfo，以便回调方法有权访问该RegisteredWaitHandle对象。
除了指定 TaskInfo 为传递给回调方法的对象外，对 RegisterWaitForSingleObject 方法的调用还指定 AutoResetEvent 任务将等待的委托、 WaitOrTimerCallback 表示 WaitProc 回调方法的委托、一秒超时间隔和多个回调。
当主线程通过调用其Set方法发出信号AutoResetEvent时，WaitOrTimerCallback将调用委托。 该方法 WaitProc 测试 RegisteredWaitHandle 以确定是否发生超时。 如果调用回调是因为等待句柄已发出信号，该方法 WaitProc 将取消注册该 RegisteredWaitHandle回调，从而停止其他回调。 如果超时，任务将继续等待。 该方法 WaitProc 通过将消息打印到控制台结束。
using namespace System;
using namespace System::Threading;
// TaskInfo contains data that will be passed to the callback
// method.
public ref class TaskInfo
{
public:
TaskInfo()
{
Handle = nullptr;
OtherInfo = "default";
}
RegisteredWaitHandle^ Handle;
String^ OtherInfo;
};
ref class Example
{
public:
// 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.
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 = static_cast<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 != nullptr )
ti->Handle->Unregister( nullptr );
}
Console::WriteLine( "WaitProc( {0}) executes on thread {1}; cause = {2}.", ti->OtherInfo, Thread::CurrentThread->GetHashCode(), cause );
}
};
int main()
{
// The main thread uses AutoResetEvent to signal the
// registered wait handle, which executes the callback
// method.
AutoResetEvent^ ev = gcnew AutoResetEvent( false );
TaskInfo^ ti = gcnew 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, gcnew WaitOrTimerCallback( Example::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.
return 0;
}
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
注解
如果 waitObject 指定，则仅当成功注销时才 RegisteredWaitHandle 发出信号。 如果在执行时 Unregister 正在进行回调方法， waitObject 则在回调方法完成之前不会发出信号。 具体而言，如果回调方法执行 Unregister， waitObject 则在回调方法完成之前不会发出信号。