Question

What is the standard nowadays when one needs a thread safe collection (e.g. Set).
Do I synchronize it myself, or is there an inherently thread safe collection?

Answer 1

The .NET 4.0 Framework introduces several thread-safe collections in the System.Collections.Concurrent Namespace:

ConcurrentBag<T>
      Represents a thread-safe, unordered collection of objects.

ConcurrentDictionary<TKey, TValue>
    Represents a thread-safe collection of key-value pairs that can be accessed by multiple threads concurrently.

ConcurrentQueue<T>
    Represents a thread-safe first in-first out (FIFO) collection.

ConcurrentStack<T>
    Represents a thread-safe last in-first out (LIFO) collection.

---

Other collections in the .NET Framework are not thread-safe by default and need to be locked for each operation:

lock (mySet)
{
    mySet.Add("Hello World");
}