C# multi-threaded reading of unmodifiable collections

Question

I have a dictionary which is filled once in a static constructor and stays unchanged ever since. I want multiple threads to be able to read values from this collection. Do I need any locking here?

Answer 1

According to Microsoft's documentation, the Dictionary class can support multiple readers concurrently, as long as the collection is not modified. Therefore, no locks are required.

Answer 2

No. Locking is only required when you have the possibility of interleaving multiple writes or writes with reads. Reading only, with no changes at all doesn't introduce the possibility of what one thread is doing affecting what another thread is doing.

Note that this requires no writes, at all. If, say, you're using an object and reading it somehow modifies the internal state of the object as a side effect, then you'd need to have locking still.