I need a HashSet that preserves insertion ordering, are there any implementations of this in the framework?
4 Answers
If you need constant complexity of Add, Remove, Contains and order preservation, then there's no such collection in .NET Framework 4.5.
If you're okay with 3rd party code, take a look at my repository (permissive MIT license): https://github.com/OndrejPetrzilka/Rock.Collections
There's OrderedHashSet<T> collection:
- based on classic
HashSet<T>source code (from .NET Core) - preserves order of insertions and allows manual reordering
- features reversed enumeration
- has same operation complexities as
HashSet<T> AddandRemoveoperations are 20% slower compared toHashSet<T>- consumes 8 more bytes of memory per item
You can use OrderedDictionary to preserve the order of insertion. But beware of the cost of Removing items (O(n)).
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