Why call SignOut(DefaultAuthenticationTypes.ExternalCookie) before use of ApplicationCookie with ASP.Net Identity?

Question

Why does this example call the SignOut for ExternalCookie before signing in with an ApplicationCookie? Is it just a way to make sure the authentication information is clean?

Answer 1

Its basically cleanup, the external cookie should get cleared eventually, its only needed to store the claims returned from google/fb/twitter etc such that app can pull whatever data it needs before signing the user. So SignIn is a good safe place to clear that external data.