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RegisteredWaitHandle Class

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

Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)

'Declaration
<ComVisibleAttribute(True)> _
Public NotInheritable Class RegisteredWaitHandle
	Inherits MarshalByRefObject
'Usage
Dim instance As RegisteredWaitHandle

/** @attribute ComVisibleAttribute(true) */ 
public final class RegisteredWaitHandle extends MarshalByRefObject
ComVisibleAttribute(true) 
public final class RegisteredWaitHandle extends MarshalByRefObject

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

    <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

import System.*;
import System.Threading.*;
import System.Threading.Thread;

// TaskInfo contains data that will be passed to the callback
// method.
public class TaskInfo
{
    public RegisteredWaitHandle handle = null;
    public String otherInfo = "default";
} //TaskInfo

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.
    } //main

    // 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, boolean 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, 
            String.valueOf(Thread.get_CurrentThread().GetHashCode()),cause);
    } //WaitProc
} //Example

System.Object
   System.MarshalByRefObject
    System.Threading.RegisteredWaitHandle

This type is safe for multithreaded operations.

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0
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