Synchronization constructs of four categories

Simple blocking methods

These wait for another thread to finish or for a period of time to elapse. Sleep, Join, and Task.Wait are simple blocking methods.

Locking constructs

These limit the number of threads that can perform some activity or execute a section of code at a time.Exclusive locking constructs are most common — these allow just one thread in at a time, and allow competing threads to access common data without interfering with each other. The standard exclusive locking constructs are lock (Monitor.Enter/Monitor.Exit), Mutex, and SpinLock. The nonexclusive locking constructs areSemaphore, SemaphoreSlim, and the reader/writer locks.

Signaling constructs

These allow a thread to pause until receiving a notification from another, avoiding the need for inefficient polling. There are two commonly used signaling devices: event wait handles and Monitor’s Wait/Pulse methods. Framework 4.0 introduces the CountdownEvent and Barrier classes.

Nonblocking synchronization constructs

These protect access to a common field by calling upon processor primitives. The CLR and C# provide the following nonblocking constructs: Thread.MemoryBarrier, Thread.VolatileRead, Thread.VolatileWrite, thevolatile keyword, and the Interlocked class.

Blocking is essential to all but the last category.