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Asked: 2026-05-20T06:35:02+00:00

I have four level data structure defined like this: Dictionary<Type1, Dictionary<Type2, Dictionary<Type3, List<Type4>>>> The

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I have four level data structure defined like this:

Dictionary<Type1, Dictionary<Type2, Dictionary<Type3, List<Type4>>>>

The whole thing is encapsulated in a class which also maintains thread-safety. Currently it just locks whole collection while it reads/manipulates the data (reading is by orders of magnitude more common than writing).

I was thinking of replacing the Dictionary with ConcurrentDictionary and List with ConcurrentBag (its items don’t have to be ordered).

If I do so, can I just eliminate the locks and be sure the concurrent collections will do their job correctly?

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1 Answer

  1. Editorial Team

    The concurrent collections will prevent data corruption and crashes, but the code won’t be semantically equivalent to your current one. For example, if you iterate one of the concurrent dictionaries, some of the items may belong to different updates:

    The enumerator returned from the
    dictionary is safe to use concurrently
    with reads and writes to the
    dictionary, however it does not
    represent a moment-in-time snapshot of
    the dictionary. The contents exposed
    through the enumerator may contain
    modifications made to the dictionary
    after GetEnumerator was called.

    If you want to maintain the exact behavior you have now, yet save on the cost of locking, you may want to lock with ReaderWriterLockSlim which is especially suited for cases with more reads than writes.

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