Hi @Terry.Humphries,
Thanks for reaching out to the Auth0 Community!
First, have you taken a look at our Add Login Using the Authorization Code Flow with PKCE documentation?
This should provide you with guidelines on adopting the Authorization Code Flow with PKCE in your .NET application.
Moreover, you could check out our Developer Hub for an example that suits your need. And if there isn’t an exact example, you can request for a specific example through this Developer Hub Community Post
Hoped this helps!
Please let me know if you have any additional questions.
Thank you.