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WaitHandle.WaitAll Method (WaitHandle[], TimeSpan)


Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval.

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

public static bool WaitAll(
	WaitHandle[] waitHandles,
	TimeSpan timeout


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

A TimeSpan that represents the number of milliseconds to wait, or a TimeSpan that represents -1 milliseconds, to wait indefinitely.

Return Value

Type: System.Boolean

true when every element in waitHandles has received a signal; otherwise, false.

Exception Condition

The waitHandles parameter is null.


One or more of the objects in the waitHandles array is null.


waitHandles is an array with no elements.


In the .NET for Windows Store apps or the , catch the base class exception, ArgumentException, instead.

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.


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.

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 WaitAll method is not supported on threads that have STAThreadAttribute.

The maximum value for timeout is Int32.MaxValue.

Calling this method overload is the same as calling the WaitAll(WaitHandle[], TimeSpan, Boolean) overload and specifying false for exitContext.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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