WaitHandle Class
Encapsulates operating system–specific objects that wait for exclusive access to shared resources.
System.MarshalByRefObject
System.Threading.WaitHandle
System.Threading.EventWaitHandle
System.Threading.Mutex
System.Threading.Semaphore
Assembly: mscorlib (in mscorlib.dll)
The WaitHandle type exposes the following members.
| Name | Description | |
|---|---|---|
![]() ![]() | Handle | Obsolete. Gets or sets the native operating system handle. |
![]() | SafeWaitHandle | Gets or sets the native operating system handle. |
| Name | Description | |
|---|---|---|
![]() ![]() | Close | When overridden in a derived class, releases all resources held by the current WaitHandle. |
![]() | CreateObjRef | Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject.) |
![]() ![]() | Dispose | Releases all resources used by the current instance of the WaitHandle class. |
![]() ![]() ![]() | Dispose(Boolean) | When overridden in a derived class, releases the unmanaged resources used by the WaitHandle, and optionally releases the managed resources. |
![]() ![]() ![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() ![]() ![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() ![]() ![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() | GetLifetimeService | Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject.) |
![]() ![]() ![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | InitializeLifetimeService | Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject.) |
![]() ![]() ![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | MemberwiseClone(Boolean) | Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject.) |
![]() ![]() | SignalAndWait(WaitHandle, WaitHandle) | Signals one WaitHandle and waits on another. |
![]() ![]() | SignalAndWait(WaitHandle, WaitHandle, Int32, Boolean) | Signals one WaitHandle and waits on another, specifying a time-out interval as a 32-bit signed integer and specifying whether to exit the synchronization domain for the context before entering the wait. |
![]() ![]() | SignalAndWait(WaitHandle, WaitHandle, TimeSpan, Boolean) | Signals one WaitHandle and waits on another, specifying the time-out interval as a TimeSpan and specifying whether to exit the synchronization domain for the context before entering the wait. |
![]() ![]() ![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
![]() ![]() | WaitAll(WaitHandle()) | Waits for all the elements in the specified array to receive a signal. |
![]() ![]() | WaitAll(WaitHandle(), Int32) | Waits for all the elements in the specified array to receive a signal, using an Int32 value to specify the time interval. |
![]() ![]() | WaitAll(WaitHandle(), TimeSpan) | Waits for all the elements in the specified array to receive a signal, using a TimeSpan value to specify the time interval. |
![]() ![]() | WaitAll(WaitHandle(), Int32, Boolean) | Waits for all the elements in the specified array to receive a signal, using an Int32 value to specify the time interval and specifying whether to exit the synchronization domain before the wait. |
![]() ![]() | WaitAll(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. |
![]() ![]() | WaitAny(WaitHandle()) | Waits for any of the elements in the specified array to receive a signal. |
![]() ![]() | WaitAny(WaitHandle(), Int32) | Waits for any of the elements in the specified array to receive a signal, using a 32-bit signed integer to specify the time interval. |
![]() ![]() | WaitAny(WaitHandle(), TimeSpan) | Waits for any of the elements in the specified array to receive a signal, using a TimeSpan to specify the time interval. |
![]() ![]() | WaitAny(WaitHandle(), Int32, Boolean) | Waits for any of the elements in the specified array to receive a signal, using a 32-bit signed integer to specify the time interval, and specifying whether to exit the synchronization domain before the wait. |
![]() ![]() | WaitAny(WaitHandle(), TimeSpan, Boolean) | Waits for any of the elements in the specified array to receive a signal, using a TimeSpan to specify the time interval and specifying whether to exit the synchronization domain before the wait. |
![]() ![]() ![]() | WaitOne | Blocks the current thread until the current WaitHandle receives a signal. |
![]() | WaitOne(Int32) | Blocks the current thread until the current WaitHandle receives a signal, using a 32-bit signed integer to specify the time interval. |
![]() | WaitOne(TimeSpan) | Blocks the current thread until the current instance receives a signal, using a TimeSpan to specify the time interval. |
![]() ![]() | WaitOne(Int32, Boolean) | Blocks the current thread until the current WaitHandle receives a signal, using a 32-bit signed integer to specify the time interval and specifying whether to exit the synchronization domain before the wait. |
![]() | WaitOne(TimeSpan, Boolean) | Blocks the current thread until the current instance receives a signal, using a TimeSpan to specify the time interval and specifying whether to exit the synchronization domain before the wait. |
| Name | Description | |
|---|---|---|
![]() ![]() ![]() | InvalidHandle | Represents an invalid native operating system handle. This field is read-only. |
![]() ![]() | WaitTimeout | Indicates that a WaitAny operation timed out before any of the wait handles were signaled. This field is constant. |
This class is typically used as a base class for synchronization objects. Classes derived from WaitHandle define a signaling mechanism to indicate taking or releasing access to a shared resource, but use the inherited WaitHandle methods to block while waiting for access to shared resources.
Use the static methods of this class to block a thread until one or more synchronization objects receive a signal.
WaitHandle implements the Dispose pattern. See Implementing Finalize and Dispose to Clean Up Unmanaged Resources. When you derive from WaitHandle, use the SafeWaitHandle property to store your native handle operating system handle. You do not need to override the protected Dispose method unless you use additional unmanaged resources.
The following code example shows how two threads can do background tasks while the Main thread waits for the tasks to complete using the static WaitAny and WaitAll methods of the WaitHandle class.
Imports System Imports System.Threading NotInheritable Public Class App ' Define an array with two AutoResetEvent WaitHandles. Private Shared waitHandles() As WaitHandle = _ {New AutoResetEvent(False), New AutoResetEvent(False)} ' Define a random number generator for testing. Private Shared r As New Random() <MTAThreadAttribute> _ Public Shared Sub Main() ' Queue two tasks on two different threads; ' wait until all tasks are completed. Dim dt As DateTime = DateTime.Now Console.WriteLine("Main thread is waiting for BOTH tasks to complete.") ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(0)) ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(1)) WaitHandle.WaitAll(waitHandles) ' The time shown below should match the longest task. Console.WriteLine("Both tasks are completed (time waited={0})", _ (DateTime.Now - dt).TotalMilliseconds) ' Queue up two tasks on two different threads; ' wait until any tasks are completed. dt = DateTime.Now Console.WriteLine() Console.WriteLine("The main thread is waiting for either task to complete.") ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(0)) ThreadPool.QueueUserWorkItem(AddressOf DoTask, waitHandles(1)) Dim index As Integer = WaitHandle.WaitAny(waitHandles) ' The time shown below should match the shortest task. Console.WriteLine("Task {0} finished first (time waited={1}).", _ index + 1,(DateTime.Now - dt).TotalMilliseconds) End Sub 'Main Shared Sub DoTask(ByVal state As [Object]) Dim are As AutoResetEvent = CType(state, AutoResetEvent) Dim time As Integer = 1000 * r.Next(2, 10) Console.WriteLine("Performing a task for {0} milliseconds.", time) Thread.Sleep(time) are.Set() End Sub 'DoTask End Class 'App ' This code produces output similar to the following: ' ' Main thread is waiting for BOTH tasks to complete. ' Performing a task for 7000 milliseconds. ' Performing a task for 4000 milliseconds. ' Both tasks are completed (time waited=7064.8052) ' ' The main thread is waiting for either task to complete. ' Performing a task for 2000 milliseconds. ' Performing a task for 2000 milliseconds. ' Task 1 finished first (time waited=2000.6528).
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

