C#: Do I have to make ArrayList synchronized if multiple threads only read it

Question

I'm using static ArrayList in a class to store information about non-updatable database fields. I'm planing to initialize it in constructor once (init method call guarded by lock in constructor). After that multiple threads check if arraylist Contains a field. Do I have to control this read access in any way? For example by calling ArrayList.Synchronized.

Answer 1

No, as long as you're reading you can just have at it.

Answer 2

No. Synchronisation is only required for stateful objects where your are going to change the state.

Answer 3

No (and you shouldnt need to when creating it either as long as you do it in the static constructor, which has an implicit multithread lock - if you're not in a position to do that, you probably will want to lock). There's a ReaderWriterLockSlim if you can use to control access if you do end up needing to to R/W access though.

Answer 4

No, but consider wrapping it in a ReadOnlyCollection to make sure none of the threads can modify it.

Edit: However, to do this, you'd need to make the list a List<T> rather than an ArrayList.

Answer 5

For the initial creation of your List you could consider using a static constructor. This will only be called once on the first reference to the type.