Chapter 7, lesson 2: Sharing Data.

• We can share data bet. multiple threads.
• multithreading - multiple thredas might be interrogating our objs simult.
• Interlocked.Increment - adds 1 to value as atomic operation.
• Interlocked Class - only works with small number of .NET types.

Syncronization Locks

• Synch locks - to allow one to synch. access to objects in .NET. Can synch access to your own classes + treat larger sections of code as atomic.
• deadlocks - be careful!!

Other Synch. Mthds.

• ReaderWriterLock class - lock access to readers and writers separately - allow mult. concurrent readers but only a sinlge writer.
• To acquire a reader lock:
• 1) Instance of ReaderWriterLock class - to be shared across any threads.
• 2) try/catch block - catch ApplicationException - where acquisition of reader lock fails.
• 3) acquire lock - ReaderWriterLock.AcquireReaderLock.
• 4) try/finally - to hold any read code. thread-safe read in try, release lock in finally.
• To acquire a wrtier lock - analogous.

• Windows kernel objs - Mutex, Semaphore, Event.
• Much slower than using Monitor.
• When to use?:
• 1) Mutex - allows synch. across AppDomain and process boudaries.
• 2) Semaphore - throttles access to a resource to a set no. of threads.
• 3) Event - provides a way to notify mult. threads - across AppDomain and process boundaries - that some event has occurred.

• Mutex
• 1) create instance of Mutex to be shared across any threads - Mutex m = new Mutex();
• 2) WiatOne - to wait until lock is available.
• 3) try/finally - try - do thread-safe work - finally - release lock.