This is a port of Uber's H3 library to C# with most of the polygon functionality based on NetTopologySuite instead of in-library implementations. It supports netstandard2.0, netstandard2.1, net6.0 and is (mostly) based on release 4.0.0 of the C library.
H3 is a geospatial indexing system using a hexagonal grid that can be (approximately) subdivided into finer and finer hexagonal grids, combining the benefits of a hexagonal grid with S2's hierarchical subdivisions.
Available on nuget.org as pocketken.H3.
PM> Install-Package pocketken.H3 -Version 4.0.0
See CHANGES.md for a list of changes between releases.
Upstream documentation is available at https://h3geo.org/. Basic getting-started documentation for this port of the library is available here. I have tried to make the library work and feel more "C# like" using classes, operators, extension methods, enumerables vs. arrays and so on, but some things may be implemented more or less as straight ports of the upstream library.
While the majority of the core H3 API should be here in one form or another, there's still the odd gap in terms of documentation and tests to validate behaviour vs. upstream. PRs to improve code, tests and documentation are definitely welcome and appreciated, although please keep in mind I am quite busy these days and may be a bit slow to respond. Sorry in advance!
See these likely-out-of-date benchmarks, or you can run them yourself - e.g.:
dotnet run --configuration Release --project .\test\H3.Benchmarks\H3.Benchmarks.csproj --join --framework net6.0