ThreadPool.UnsafeRegisterWaitForSingleObject Method (WaitHandle, WaitOrTimerCallback, Object, UInt32, Boolean)
Registers a delegate to wait for a WaitHandle, specifying a 32-bit unsigned integer for the time-out in milliseconds.
Assembly: mscorlib (in mscorlib.dll)
[CLSCompliantAttribute(false)] [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.NoFlags|SecurityPermissionFlag.ControlEvidence|SecurityPermissionFlag.ControlPolicy)] public static RegisteredWaitHandle UnsafeRegisterWaitForSingleObject( WaitHandle waitObject, WaitOrTimerCallback callBack, Object state, uint millisecondsTimeOutInterval, bool executeOnlyOnce )
- Type: System.Threading.WaitHandle
- Type: System.Threading.WaitOrTimerCallback
The delegate to call when the waitObject parameter is signaled.
- Type: System.Object
The object that is passed to the delegate.
- Type: System.UInt32
The time-out in milliseconds. If the millisecondsTimeOutInterval parameter is 0 (zero), the function tests the object's state and returns immediately. If millisecondsTimeOutInterval is -1, the function's time-out interval never elapses.
- Type: System.Boolean
true to indicate that the thread will no longer wait on the waitObject parameter after the delegate has been called; false to indicate that the timer is reset every time the wait operation completes until the wait is unregistered.
Unlike the RegisterWaitForSingleObject method, UnsafeRegisterWaitForSingleObject does not propagate the calling stack to the worker thread. This allows code to lose the calling stack and thereby to elevate its security privileges.
Using UnsafeRegisterWaitForSingleObject could inadvertently open up a security hole. Code access security bases its permission checks on the permissions of all the callers on the stack. When work is queued on a thread pool thread using UnsafeRegisterWaitForSingleObject, the stack of the thread pool thread will not have the context of the actual callers. Malicious code might be able exploit this to avoid permission checks.
Using a Mutex for waitObject does not provide mutual exclusion for the callbacks because the underlying Win32 API uses the default WT_EXECUTEDEFAULT flag, so each callback is dispatched on a separate thread pool thread.
When you are finished using the RegisteredWaitHandle that is returned by this method, call its RegisteredWaitHandle.Unregister method to release references to the wait handle. We recommend that you always call the RegisteredWaitHandle.Unregister method, even if you specify true for executeOnlyOnce. Garbage collection works more efficiently if you call the RegisteredWaitHandle.Unregister method instead of depending on the registered wait handle's finalizer.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.