active-directory-dotnet-webapp-webapi-multitenant-openidconnect | NET 4.5 MVC SaaS web app | Azure library

The Azure AD multitenancy system is predicated on all participants having an Azure AD tenant, given that it relies on the 1) the endpoints following the exact same behavior, modulo parameters that differentiate across orgs and 2) apps relying on a common identity configuration backend, which allows dynamic provisioning with a simple user consent operation (as opposed to the federated provisioning required when you can't rely on such a common base). Azure AD B2C will allow you to aggregate multiple identity providers, supplying you with a single integration point. Whether that qualifies as multi tenant will depend on how you leverage the feature; out of the box, that's more similar to a classic federation provider/intermediary role. For more details, see https://docs.microsoft.com/en-us/azure/active-directory-b2c/active-directory-b2c-overview-custom.