Please tell me how can I update the access_token from the NET c # application. Or how can I get a long-lived token?
Are you referring to migrating from long-lived tokens to short-lived tokens? I would recommend reading our blog post on this process here. You can also review the examples of OAuth in our .Net documentation.
On generating a long-lived token, while they are being deprecated, you can create one from your App Console to be used in testing.
