Why use SignOut (DefaultAuthenticationTypes.ExternalCookie) before using ApplicationCookie with ASP.Net ID?

Question

Why does this example call SignOut for ExternalCookie before entering ApplicationCookie? Is this just a way to make sure the authentication data is clean? (Full example: http://www.asp.net/identity/overview/getting-started/introduction-to-aspnet-identity )

private async Task SignInAsync(ApplicationUser user, bool isPersistent) { AuthenticationManager.SignOut(DefaultAuthenticationTypes.ExternalCookie); var identity = await UserManager.CreateIdentityAsync( user, DefaultAuthenticationTypes.ApplicationCookie); AuthenticationManager.SignIn( new AuthenticationProperties() { IsPersistent = isPersistent }, identity); } 

Answer 1

Basically clearing it, an external cookie should be cleared in the end, it only needs to save claims returned from google / fb / twitter, etc., so that the application can pull out any data it needs before signing up the user. Thus, SignIn is a good safe place to clean external data.