Is ++ operation atomic in C#?

Question

I have multiple threads accessing a single Int32 variable with "++" or "--" operation.

Do we need to lock before accessing it as below?

    lock (idleAgentsLock)
    {
       idleAgents--;  //we should place it here.
    }

Or what consequences will there be if I don't do the locking?

Answer 1

It is not "atomic", not in the multi-threaded sense. However your lock protects the operation, theoretically at least. When in doubt you can of course use Interlocked.Decrement instead.