SimMetrics is a Similarity Metric Library, e.g. from edit distance's (Levenshtein, Gotoh, Jaro etc) to other metrics, (e.g Soundex, Chapman). This library support multiple .NET versions including .NET Core (NETStandard 1.x)
Why do you think that https://github.com/dotnet/machinelearning is a good alternative to SimMetrics.Net