ConcurrentDictionary and visibility

Question

I have read that ConcurrentDictionary only locks when writing, so the reads are lock free.

http://blogs.msdn.com/b/pfxteam/archive/2010/01/08/9945809.aspx reads on the dictionary are performed in a lock-free manner

But what about visibility, how do they ensure this when the reads are lock free?

Answer 1

The use of the MemoryBarrier ensures that the objects are 'published' for other threads. This does not require a lock.