Parameters

waitObject

The System.Threading.WaitHandle to register. Use a System.Threading.WaitHandle other than System.Threading.Mutex.

callBack

The delegate to call when the waitObject parameter is signaled.

state

The object that is passed to the delegate.

millisecondsTimeOutInterval

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.

executeOnlyOnce

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.

Returns

The System.Threading.RegisteredWaitHandle object that can be used to cancel the registered wait operation.

Remarks

Unlike the ThreadPool.RegisterWaitForSingleObject(WaitHandle, WaitOrTimerCallback, object, uint, bool) method, ThreadPool.UnsafeRegisterWaitForSingleObject(WaitHandle, WaitOrTimerCallback, object, uint, bool) 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.

Note:

Using ThreadPool.UnsafeRegisterWaitForSingleObject(WaitHandle, WaitOrTimerCallback, object, uint, bool) 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 ThreadPool.UnsafeRegisterWaitForSingleObject(WaitHandle, WaitOrTimerCallback, object, uint, bool), 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 System.Threading.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 System.Threading.RegisteredWaitHandle that is returned by this method, call its RegisteredWaitHandle.Unregister(WaitHandle) method to release references to the wait handle. We recommend that you always call the RegisteredWaitHandle.Unregister(WaitHandle) method, even if you specify true for executeOnlyOnce. Garbage collection works more efficiently if you call the RegisteredWaitHandle.Unregister(WaitHandle) method instead of depending on the registered wait handle's finalizer.

Requirements