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RegisteredWaitHandle Class

Represents a handle that has been registered when calling RegisterWaitForSingleObject. This class cannot be inherited.

For a list of all members of this type, see RegisteredWaitHandle Members.

System.Object
   System.MarshalByRefObject
      System.Threading.RegisteredWaitHandle

[Visual Basic]
NotInheritable Public Class RegisteredWaitHandle
   Inherits MarshalByRefObject
[C#]
public sealed class RegisteredWaitHandle : MarshalByRefObject
[C++]
public __gc __sealed class RegisteredWaitHandle : public
   MarshalByRefObject
[JScript]
public class RegisteredWaitHandle extends MarshalByRefObject

Thread Safety

This type is safe for multithreaded operations.

Example

[Visual Basic] 
Imports System
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
    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

[C#] 
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
        );
    }
}

[C++] 
#using <mscorlib.dll>

using namespace System;
using namespace System::Threading;

// TaskInfo contains data that will be passed to the callback
// method.
public __gc class TaskInfo 
{
public:
    TaskInfo()
    {
        Handle = 0;
        OtherInfo = S"default";
    }

    RegisteredWaitHandle* Handle;;
    String* OtherInfo;
};


__gc class Example
{
    // 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 = static_cast<TaskInfo*>(state);

        String* cause = S"TIMED OUT";
        if (!timedOut) {
            cause = S"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 != 0)
                ti->Handle->Unregister(0);
        } 

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

int main() 
{
    // 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 = S"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(0, 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(S"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;
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Threading

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: Mscorlib (in Mscorlib.dll)

See Also

RegisteredWaitHandle Members | System.Threading Namespace | Thread Pooling

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