Releases the lock on an object and blocks the current thread until it reacquires the lock. If the specified time-out interval elapses, the thread enters the ready queue.
Syntax
Parameters
- obj
- millisecondsTimeout
Returns
true if the lock was reacquired before the specified time elapsed; false if the lock was reacquired after the specified time elapsed. The method does not return until the lock is reacquired.
Exceptions
Type Reason ArgumentNullException obj is null. System.Threading.SynchronizationLockException The calling thread does not own the lock for the specified object. ArgumentOutOfRangeException The value of millisecondsTimeout is negative, and not equal to Timeout.Infinite .
Remarks
This method does not return until it reacquires an exclusive lock on the obj parameter.
The thread that currently owns the lock on the specified object invokes this method in order to release the object so that another thread can access it. The caller is blocked while waiting to reacquire the lock. This method is called when the caller needs to wait for a state change that will occur as a result of another thread's operations.
The time-out ensures that the current thread does not block indefinitely if another thread releases the lock without first calling the Monitor.Pulse(object) or Monitor.PulseAll(object) method. It also moves the thread to the ready queue, bypassing other threads ahead of it in the wait queue, so that it can reacquire the lock sooner. The thread can test the return value of the Monitor.Wait(object, int) method to determine whether it reacquired the lock prior to the time-out. The thread can evaluate the conditions that caused it to enter the wait, and if necessary call the Monitor.Wait(object, int) method again.
When a thread calls Wait, it releases the lock on the object and enters the object's waiting queue. The next thread in the object's ready queue (if there is one) acquires the lock and has exclusive use of the object. The thread that invoked Wait remains in the waiting queue until either a thread that holds the lock invokes Monitor.PulseAll(object), or it is the next in the queue and a thread that holds the lock invokes Monitor.Pulse(object). However, if millisecondsTimeout elapses before another thread invokes this object's Monitor.Pulse(object) or Monitor.PulseAll(object) method, the original thread is moved to the ready queue in order to regain the lock.
If Timeout.Infinite is specified for the millisecondsTimeout parameter, this method blocks indefinitely unless the holder of the lock calls Monitor.Pulse(object) or Monitor.PulseAll(object). If millisecondsTimeout equals 0, the thread that calls Wait releases the lock and then immediately enters the ready queue in order to regain the lock.
The caller executes Wait once, regardless of the number of times Monitor.Enter(object) has been invoked for the specified object. Conceptually, the Wait method stores the number of times the caller invoked Monitor.Enter(object) on the object and invokes Monitor.Exit(object) as many times as necessary to fully release the locked object. The caller then blocks while waiting to reacquire the object. When the caller reacquires the lock, the system calls Monitor.Enter(object) as many times as necessary to restore the saved Monitor.Enter(object) count for the caller. Calling Wait releases the lock for the specified object only; if the caller is the owner of locks on other objects, these locks are not released.
A synchronized object holds several references, including a reference to the thread that currently holds the lock, a reference to the ready queue, which contains the threads that are ready to obtain the lock, and a reference to the waiting queue, which contains the threads that are waiting for notification of a change in the object's state.
The Monitor.Pulse(object), Monitor.PulseAll(object), and Wait methods must be invoked from within a synchronized block of code.
The remarks for the Monitor.Pulse(object) method explain what happens if Monitor.Pulse(object) is called when no threads are waiting.
Requirements
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0