is locking necessary for Dictionary lookup?

Question

lock(dictionaryX)
{
   dictionaryX.TryGetValue(key, out value);
}

is locking necessary while doing lookups to a Dictionary ?

THe program is

Answer 1

Yes, you have to lock if you have multithreaded updates on that dictionary. Check this great post for details: “Thread safe” Dictionary(TKey,TValue)

But since ConcurrentDictionary<> introduced you can use it either via .NET 4 or by using Rx in 3.5 (it contains System.Threading.dll with implementation for new thread-safe collections)