There's a newer version of this sample taking advantage of the Microsoft identity platform
Check it out the B2C variations of the ASP.NET Core web app incremental tutorial:
- An ASP.NET Core Web app that uses OpenID Connect to sign in users in Azure AD B2C: https://github.com/Azure-Samples/active-directory-aspnetcore-webapp-openidconnect-v2/tree/master/1-WebApp-OIDC/1-5-B2C
- An ASP.NET Core web application that can sign in a user using Azure AD B2C, get an access token using MSAL.NET and call an API: https://github.com/Azure-Samples/active-directory-aspnetcore-webapp-openidconnect-v2/tree/master/4-WebApp-your-API/4-2-B2C
If you really need to access this sample, you can navigate to the master branch, but please know that it's no longer supported.