Want to start developing custom YNAB tools using .net core ? You can use this github project as a base [https://github.com/wleme/YnabDotNetCoreStarterKit]
This project successfully implements the OAuth middleware and saves the tokens in a cookie. It then retrieves the access token every time it pulls data from their API (budgets and categories within a budget). It also leverages the new HttpClientFactory (introduced on .net core 2.1).
You need to get your own Client Id and Client Secret and update appsettings.json.
Issues ? Please go to github. PRs are also welcome.
YNAB Api doc: [https://api.youneedabudget.com/]