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I want to create a mobile app using Xamarin forms that customers (Portal users, NOT internal Users of the Dynamics CRM ) can use to access some account information related to their account.
Is there an web API that can be called that could authenticate customer portal users and also create a customer portal user within Dynamics 365?
I'm interested in your point. How did you manage ?
I haven't been able to figure out how to do this. I have asked Microsoft support and they don't know as well. Have you looked into this as well?
A solution I have seen presented by http://colinvermander.com/ was to make sure your portal uses an external authentication method and not the native email & password. If you have that implemented you can create your own webapi that uses the samen authentication and you can link your portal user to your api user based on the external authentication method.
To make sure I keep this option open in one of my implementations I'm using Azure B2C. Unfortunately I'm not able to successfully configure it at the moment. But you could also use Azure AD, Google, Facebook etc.