System.Collections.Concurrent

Added in ?
The System.Collections.Concurrent namespace has the following collections
These collections are highly optimised for high concurrency scenarios and are thread safe.

System.Collections.Concurrent.ConcurrentStack<T> 
Stack<T> 

System.Collections.Concurrent.ConcurrentQueue<T> 
Queue<T> 

System.Collections.Concurrent.ConcurrentBag<T> 

no-non concurrent equivaleent

System.Collections.Concurrent.ConcurrentDictionary<TKey, TValue> 
Dictionary<TKey, TValue>