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WaitAny Method (WaitHandle[])

WaitHandle.WaitAny Method (WaitHandle[])

Waits for any of the elements in the specified array to receive a signal.

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

static member WaitAny : 
        waitHandles:WaitHandle[] -> int


Type: System.Threading.WaitHandle[]

A WaitHandle array containing the objects for which the current instance will wait.

Return Value

Type: System.Int32
The array index of the object that satisfied the wait.


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).


The number of objects in waitHandles is greater than the system permits.


waitHandles is an array with no elements, and the .NET Framework version is 1.0 or 1.1.


The wait completed because a thread exited without releasing a mutex. This exception is not thrown on Windows 98 or Windows Millennium Edition.


waitHandles is an array with no elements, and the .NET Framework version is 2.0 or later.


The waitHandles array contains a transparent proxy for a WaitHandle in another application domain.

AbandonedMutexException is new in the .NET Framework version 2.0. In previous versions, the WaitAny method returns true if the wait completes because 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 WaitAny method throws an AbandonedMutexException only when the wait completes because of an abandoned mutex. If waitHandles contains a released mutex with a lower index number than the abandoned mutex, the WaitAny method completes normally and the exception is not thrown.


In versions of the .NET Framework earlier than version 2.0, if a thread exits or aborts without explicitly releasing a Mutex, and that Mutex is at index 0 (zero) in a WaitAny array on another thread, the index returned by WaitAny is 128 instead of 0.

This method returns when any handle is signaled. If more than one object becomes signaled during the call, the return value is the array index of the signaled object with the smallest index value of all the signaled objects. On some implementations, if more that 64 handles are passed, a NotSupportedException is thrown.

Calling this method overload is equivalent to calling the WaitAny(WaitHandle[], Int32, Boolean) method overload and specifying -1 (or Timeout.Infinite) for millisecondsTimeout and true for exitContext.

The following code example demonstrates calling the WaitAny method.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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