public override Task Authenticated(YahooAuthenticatedContext context)
        {
            context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Email));

            return base.Authenticated(context);
        }
        protected override async Task <AuthenticationTicket> AuthenticateCoreAsync()
        {
            AuthenticationProperties properties = null;

            try
            {
                var query = Request.Query;
                var protectedRequestToken = Request.Cookies[StateCookie];

                var requestToken = Options.StateDataFormat.Unprotect(protectedRequestToken);

                if (requestToken == null)
                {
                    _logger.WriteWarning("Invalid state");
                    return(null);
                }

                properties = requestToken.Properties;

                var returnedToken = query.Get("oauth_token");
                if (string.IsNullOrWhiteSpace(returnedToken))
                {
                    _logger.WriteWarning("Missing oauth_token");
                    return(new AuthenticationTicket(null, properties));
                }

                if (returnedToken != requestToken.Token)
                {
                    _logger.WriteWarning("Unmatched token");
                    return(new AuthenticationTicket(null, properties));
                }

                var oauthVerifier = query.Get("oauth_verifier");
                if (string.IsNullOrWhiteSpace(oauthVerifier))
                {
                    _logger.WriteWarning("Missing or blank oauth_verifier");
                    return(new AuthenticationTicket(null, properties));
                }

                var accessToken = await ObtainAccessTokenAsync(Options.ConsumerKey, Options.ConsumerSecret, requestToken, oauthVerifier);

                var userCard = await ObtainUserProfile(Options.ConsumerKey, Options.ConsumerSecret, accessToken, oauthVerifier);

                var context = new YahooAuthenticatedContext(Context, userCard, accessToken.UserId, accessToken.Token,
                                                            accessToken.TokenSecret)
                {
                    Identity = new ClaimsIdentity(
                        Options.AuthenticationType,
                        ClaimsIdentity.DefaultNameClaimType,
                        ClaimsIdentity.DefaultRoleClaimType)
                };

                if (!string.IsNullOrEmpty(context.UserId))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.NameIdentifier, context.UserId,
                                                        "http://www.w3.org/2001/XMLSchema#string", Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.NickName))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Name, context.NickName,
                                                        "http://www.w3.org/2001/XMLSchema#string", Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.Email))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Email,
                                                        "http://www.w3.org/2001/XMLSchema#string", Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.UserId))
                {
                    context.Identity.AddClaim(new Claim("urn:yahoo:userid", context.UserId,
                                                        "http://www.w3.org/2001/XMLSchema#string", Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.NickName))
                {
                    context.Identity.AddClaim(new Claim("urn:yahoo:nickname", context.NickName,
                                                        "http://www.w3.org/2001/XMLSchema#string", Options.AuthenticationType));
                }
                context.Properties = requestToken.Properties;

                Response.Cookies.Delete(StateCookie);

                await Options.Provider.Authenticated(context);

                return(new AuthenticationTicket(context.Identity, context.Properties));
            }
            catch (Exception ex)
            {
                _logger.WriteError("Authentication failed", ex);
                return(new AuthenticationTicket(null, properties));
            }
        }
 /// <summary>
 /// Invoked whenever Yahoo succesfully authenticates a user
 /// </summary>
 /// <param name="context">Contains information about the login session as well as the user <see cref="System.Security.Claims.ClaimsIdentity"/>.</param>
 /// <returns>A <see cref="Task"/> representing the completed operation.</returns>
 public virtual Task Authenticated(YahooAuthenticatedContext context)
 {
     return(OnAuthenticated(context));
 }
 /// <summary>
 /// Invoked whenever Yahoo successfully authenticates a user
 /// </summary>
 /// <param name="context">Contains information about the login session as well as the user <see cref="System.Security.Claims.ClaimsIdentity"/>.</param>
 /// <returns>A <see cref="Task"/> representing the completed operation.</returns>
 public virtual Task Authenticated(YahooAuthenticatedContext context)
 {
     return OnAuthenticated(context);
 }