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 need to lock the dictionary for access in a multithreaded environment. The writing to a dictionary is not atomic, so it could add the key, but not the value. In that case when you access it, you could get an exception.