To use of OAuth provider, we have to create an application first to obtain the client ID and client secret keys. We can then use these keys to authenticate our ASP.NET application by adding a middleware and specify them as discussed in the section as follows. Here are the steps to register a new application on Facebook:

1. Create an app by navigating to http://developers.facebook.com/apps and log in with your user registered Facebook ID.
2. Click on the Add a new App option and select Website (WWW).
3. Specify your app name and click on Create New Facebook App ID.
4. Specify display name, category, and Contact Email and click on Create App ID.
5. Once the application is created, you have to go through some tabs to specify basic information.
6. Specify your website URL and proceed:

7. Go to your account settings and copy the App ID and App Secret that can be used for authorization:

To authenticate with Facebook or any other external provider, we need to provide the Application ID and secret key for authorization of our application. ASP.NET Core.