Exchanged Concurrent dictionary by plain Dictionary and ReaderWriterLockSlim - now looks more safe, but maybe in future I will return to it.
Exchanged Concurrent dictionary by plain Dictionary and ReaderWriterLockSlim - now looks more safe, but maybe in future I will return to it.

karasek/BTDB,Bobris/BTDB,yonglehou/BTDB,klesta490/BTDB