Energistics.DataAccess.EnumValue isn't thread-safe

[cory-hrh]

Summary

If you are creating new EnumValue instances on multiple threads there is a possibility of collisions causing run-time failures.

This was observed when creating Energistics.DataAccess.WITSML141.QualifierType instances on multiple threads threw an InvalidOperationException as you cannot modify a collection when iterating over it.

Technical details

The issue is in the Register() method in Energistics.DataAccess.EnumValue. This accesses a static ConcurrentDictionary<Type, List<EnumValue>> instance.
The issue is that although the ConcurrentDictionary is thread-safe the List it returns is not.

The Register() method both iterates over this List and can add new elements to it.
Therefore you can have Thread A iterating over the list while Thread B simultaneously modifies it causing Thread A to throw an exception.