Azure AD multi tenant authentication - how to whitelist specific tenants?

Question

What I want to achieve

I'm building a web app with an SPA front end that will be hosted in Azure and which will use Azure AD authentication.

I want all users from my main tenant to be able to access the app without having to be invited.

I want to be able to invite external users to access the app.

My plan

Create a B2C tenant in single tenant mode. External users will be invited to this.

In the B2C tenant create a custom sign up policy that permits only users in the main tenant to sign themselves up to the B2C tenant.

Questions

Will this work?

Is this the best approach?

Answer 1

If by invite you mean send an email, B2C out of the box does not have an invite feature.

You'd have to write this yourself and use your own email provider.

In terms of whitelisting, refer to the B2C samples here, here and here.