System.Threading.WaitHandle.WaitOne Method

Blocks the current thread until the current System.Threading.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.


public virtual bool WaitOne (int millisecondsTimeout, bool exitContext)


The number of milliseconds to wait, or Timeout.Infinite (-1) to wait indefinitely.
true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it afterward; otherwise, false.


true if the current instance receives a signal; otherwise, false.


If millisecondsTimeout is zero, the method does not block. It tests the state of the wait handle and returns immediately.

System.Threading.AbandonedMutexException is new in the .NET Framework version 2.0. In previous versions, the erload:System.Threading.WaitHandle.WaitOne 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 caller of this method blocks until the current instance receives a signal or a time-out occurs. Use this method to block until a System.Threading.WaitHandle receives a signal from another thread, such as is generated when an asynchronous operation completes. For more information, see the IAsyncResult interface.

Override this method to customize the behavior of derived classes.

Notes on Exiting the Context

The exitContext parameter has no effect unless the WaitHandle.WaitOne(int, bool) 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 does not derive 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 WaitHandle.WaitOne(int, bool) method. The thread returns to the original nondefault context after the call to the WaitHandle.WaitOne(int, bool) method completes.

This can be useful when the context-bound class has System.Runtime.Remoting.Contexts.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 WaitHandle.WaitOne(int, bool) 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 WaitHandle.WaitOne(int, bool) method returns, the thread that made the call must wait to reenter the synchronization domain.


Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0,,