Not sure where the [comedy lies](https://sqlite.org/forum/forumpost/d4deebf85a?raw) but I found a [worked example here](https://www.metalliccode.com/writing-new-sql-functions) which I've successfully adapted to work with C#.
Not sure where the [comedy lies](https://sqlite.org/forum/forumpost/d4deebf85a?raw) but I found a [worked example here](https://www.metalliccode.com/writing-new-sql-functions) which I've successfully adapted to work with C#.