SQLite-net is an open source, minimal library to allow .NET and Mono applications to store data in SQLite 3 databases. The benefit of using SQLite as your database is you don't require any server to run it. Which makes it a good choice for standalone applications. SQLite is small in size, fast and reliable.
SQLite download page : https://sqlite.org/download.html
sqlite-net github : https://github.com/praeclarum/sqlite-net