I basically don't understand what resource is locked when AcquireReaderLock or AcquireWriterLock is called. You don't get to specify it yourself. MSDN help is no good here.

As I understand it, there is no specific resource associated with a ReaderWriterLock. The lock is just, er, a lock. You are responsible for acquiring and releasing or otherwise managing the lock which your threads, by convention, serialize their access to your resource through.

A ReaderWriterLock may be more efficient than other locks (e.g. mutex), if you have threads reading and some (fewer) threads writing the resource. Since the lock has distinct semantics for locking reads or writes separately, with careful design you may gain a measure of throughput over another form of lock which would single thread the access to the resource without regard to whether the access is read or write.

Jeff Mason
Custom Apps, Inc.
www.custom-apps.com