This request is based upon the new Visual Studio 2013 integration of Asp.net Identity stuff. I have seen some of the posts regarding this question for MVC, but for the life of
Ok, I know you said you want to know how to do WITHOUT MVC, and while I cannot answer that directly, I can tell you that I had similar issues with MVC, and how I resolved it. Hopefully that points you in the right direction in Web Forms.
The key bits was the following:
After you have logged in using the external provider you are directed to a page where you register the new user. After the postback from that I had to add a line to first of all get the ClaimsIdentity again:
ClaimsIdentity claimsIdentity =
await AuthenticationManager.GetExternalIdentityAsync(DefaultAuthenticationTypes.ExternalCookie);
Without the call to this line above it did not work for me at all, so maybe that is where your problem lies.
Once I had the ClaimsIdentity you can iterate through the collection of claims on the Claims property of the identity. This should include the Facebook token you added in the OnAuthenticated callback delegate. All you have to do then is call UserManager.AddClaimAsync() to add it to the Claims database table.
For more info look at my AccountController class at https://github.com/beabigrockstar/AspNetIdentitySocialProfileImage/blob/master/Controllers/AccountController.cs
Look specifically at the method ExternalLoginConfirmation(ExternalLoginConfirmationViewModel model, string returnUrl) and the call to StoreAuthTokenClaims(), and then of course the process I follow in StoreAuthTokenClaims()
Hope that this can somehow help you in WebForms.