Awesome

XamarinFormsOIDCSample

Xamarin Forms OAuth 2.0 / OpenID Connect Sample with IdentityServer3

Related blog post: https://www.kevindockx.com/working-with-oauth2-and-openid-connect-from-a-xamarin-forms-application-using-identityserver3/

Note: in the sample, I deployed IdSrv & the API to Azure. If you want to run this locally, you have to make sure that you can access these from your Xamarin application. To enable this with IIS Express, have a look at https://azure.microsoft.com/en-us/documentation/articles/mobile-services-dotnet-backend-how-to-configure-iis-express/

Even though that post is aimed at Azure Mobile Services, it nicely explains the steps you have to take to configure IIS Express (& your machine) so you can access services hosted on your IIS Express from a Xamarin application, running in an emulator.