How to write conditional lock in C #?

Question

The fact is that I used the instruction to protect an important part of my code, but now I understand that I can allow the simultaneous execution of this critical code - this is the fulfillment of certain conditions.
Is there any way to set the lock?

Answer 1

Action doThatThing = someMethod; if (condition) { lock(thatThing) { doThatThing(); } } else { doThatThing(); } 

Answer 2

I think this question yells "race condition!". What should I do if the condition goes from true to false right after checking, but before the stream gets to the critical section of the code? Or while the thread is in the process of executing it?

Answer 3

 bool locked = false; if (condition) { Monitor.Enter(lockObject); locked = true; } try { // possibly critical section } finally { if (locked) Monitor.Exit(lockObject); } 

EDIT: yes, there is a race condition if you can’t assure that the condition is constant when entering streams.

Answer 4

I'm not a thread specialist, but it looks like you might find something like this (double check). The idea is to check the status both before and after acquiring the lock.

 private static object lockHolder = new object(); if (ActionIsValid()) { lock(lockHolder) { if (ActionIsValid()) { DoSomething(); } } } 

Answer 5

In fact, in order to avoid the race condition, I would like to use ReaderWriterLockSlim here - to consider simultaneous access as a read lock and exclusive access as a write lock. Thus, if the conditions change, you will not have some inappropriate code still performing blind action in the region (under the false assumption that it is safe); bit verbose, but (formatted for space):

  if (someCondition) { lockObj.EnterReadLock(); try { Foo(); } finally { lockObj.ExitReadLock(); } } else { lockObj.EnterWriteLock(); try { Foo(); } finally { lockObj.ExitWriteLock(); } } 

Answer 6

Use the Double-Checked Lock Pattern as suggested above. what's the IMO trick :)

make sure your lock object is static as indicated in the not.that.dave.foley.myopenid.com example.

Answer 7

I assume you have code that looks something like this:

 private Monkey GetScaryMonkey(int numberOfHeads){ Monkey ape = null; lock(this) { ape = new Monkey(); ape.AddHeads(numberOfHeads); } return ape; } 

To make this condition, you could not just do this:

 private Monkey GetScaryMonkey(int numberOfHeads){ if ( numberOfHeads > 1 ) { lock(this) { return CreateNewMonkey( numberOfHeads ); } } return CreateNewMonkey( numberOfHeads ); } 

Should work, no?