app.UseFacebookAuthentication(
   appId: "xxxxxx",
   appSecret: "xxxxxx");

app.UseGoogleAuthentication(new GoogleOAuth2AuthenticationOptions()
{
    ClientId = "ssssss",
    ClientSecret = "sssss"
});

public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
{
    var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
    if (loginInfo == null)
    {
        return RedirectToAction("Login");
    }

    // Sign in the user with this external login provider if the user already has a login
    var result = await SignInManager.ExternalSignInAsync(loginInfo, isPersistent: false);
    switch (result)
    {
        case SignInStatus.Success:
            return RedirectToLocal(returnUrl);
        case SignInStatus.LockedOut:
            return View("Lockout");
        case SignInStatus.RequiresVerification:
            return RedirectToAction("SendCode", new { ReturnUrl = returnUrl, RememberMe = false });
        case SignInStatus.Failure:
        default:
            // If the user does not have an account, then prompt the user to create an account
            ViewBag.ReturnUrl = returnUrl;
            ViewBag.LoginProvider = loginInfo.Login.LoginProvider;
            var viewModel = new ExternalLoginConfirmationViewModel
            {
                Email = loginInfo.Email
            };
            ViewBag.Title = "Register";

            return View("ExternalLoginConfirmation", viewModel);
    }
}