WaitHandle.WaitAll Method (WaitHandle, TimeSpan, Boolean)
Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval, and specifying whether to exit the synchronization domain before the wait.
Assembly: mscorlib (in mscorlib.dll)
static member WaitAll : waitHandles:WaitHandle * timeout:TimeSpan * exitContext:bool -> bool
- Type: System.Threading.WaitHandle
A WaitHandle array containing the objects for which the current instance will wait. This array cannot contain multiple references to the same object.
- Type: System.TimeSpan
- Type: System.Boolean
true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it afterward; otherwise, false.
Return ValueType: System.Boolean
true when every element in waitHandles has received a signal; otherwise false.
The waitHandles parameter is a null reference (Nothing in Visual Basic).
One or more of the objects in the waitHandles array is a null reference (Nothing in Visual Basic).
waitHandles is an array with no elements and the .NET Framework version is 2.0 or later.
The waitHandles array contains elements that are duplicates.
The number of objects in waitHandles is greater than the system permits.
The STAThreadAttribute attribute is applied to the thread procedure for the current thread, and waitHandles contains more than one element.
waitHandles is an array with no elements and the .NET Framework version is 1.0 or 1.1.
timeout is a negative number other than -1 milliseconds, which represents an infinite time-out.
timeout is greater than Int32.MaxValue.
The wait terminated because a thread exited without releasing a mutex. This exception is not thrown on Windows 98 or Windows Millennium Edition.
The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.
If timeout is zero, the method does not block. It tests the state of the wait handles and returns immediately.
AbandonedMutexException is new in the .NET Framework version 2.0. In previous versions, the WaitAll method returns true when a mutex is abandoned. An abandoned mutex often indicates a serious coding error. In the case of a system-wide mutex, it might indicate that an application has been terminated abruptly (for example, by using Windows Task Manager). The exception contains information useful for debugging.
The WaitAll method returns when the wait terminates, which means either all the handles are signaled or a time-out occurs. On some implementations, if more than 64 handles are passed, a NotSupportedException is thrown. If the array contains duplicates, the call will fail.
The maximum value for timeout is Int32.MaxValue.
Notes on Exiting the Context
The exitContext parameter has no effect unless the WaitAll method is called from inside a nondefault managed context. This can happen if your thread is inside a call to an instance of a class derived from ContextBoundObject. Even if you are currently executing a method on a class that is not derived from ContextBoundObject, like String, you can be in a nondefault context if a ContextBoundObject is on your stack in the current application domain.
When your code is executing in a nondefault context, specifying true for exitContext causes the thread to exit the nondefault managed context (that is, to transition to the default context) before executing the WaitAll method. It returns to the original nondefault context after the call to the WaitAll method completes.
This can be useful when the context-bound class has SynchronizationAttribute. In that case, all calls to members of the class are automatically synchronized, and the synchronization domain is the entire body of code for the class. If code in the call stack of a member calls the WaitAll method and specifies true for exitContext, the thread exits the synchronization domain, allowing a thread that is blocked on a call to any member of the object to proceed. When the WaitAll method returns, the thread that made the call must wait to reenter the synchronization domain.
The following code example shows how to use the thread pool to asynchronously create and write to a group of files. Each write operation is queued as a work item and signals when it is finished. The main thread waits for all the items to signal and then exits.