Sustainsys/Saml2

@mlindegarde and @AndersAbel thank you for your input. There are a couple methods there that I don't have a great understanding how they work, in either way here's what I've done adjusting your code to mine. FYI: this project is a legacy Asp.Net Web App (non-MVC).

in my Global.asax

    void Application_BeginRequest(object sender, EventArgs e) {
        Saml2Config.Initialize();
    }

In the Sam2Config file:

    public class Saml2Config {
        private static bool _alreadyInitialized;
        private static readonly object Lock = new object();
        private static NLog.Logger _logger = NLog.LogManager.GetCurrentClassLogger();
        public static void Initialize() {
            if (_alreadyInitialized) {
                return;
            }

            lock (Lock) {
                if (_alreadyInitialized) {
                    return;
                }

                spOptions = Options.FromConfiguration.SPOptions;

                // Get list of IdentityProviders
                var saml2IdentityProvidersRepository = new Saml2IdentityProvidersRepository();
                var saml2IdentityProviders = saml2IdentityProvidersRepository.FindByServiceProviderEntityId(spOptions.EntityId.Id, x => x.Saml2BindingType).OrderBy(x => x.OrderPreference);

                Options.FromConfiguration.Notifications.SelectIdentityProvider = (id, data) => GetProvider(saml2IdentityProviders, id, data, Options.FromConfiguration, _logger);
                Options.FromConfiguration.Notifications.GetIdentityProvider = (id, data, options) => GetProvider(saml2IdentityProviders, id, data, options, _logger);

                saml2IdentityProvidersRepository.Dispose();
                _alreadyInitialized = true;
            }
        }

        private static IdentityProvider GetProvider(IQueryable<Saml2IdentityProvider> identityProviderStore, EntityId id, IDictionary<string, string> data, IOptions options, ILogger logger) {
            var identityProvider = identityProviderStore.FirstOrDefault(x => x.IsActive && x.IdentityProviderEntityId.Equals(id.Id));

            if (identityProvider == null) {
                return null;
            }

            var idpEntityId = new EntityId(identityProvider.IdentityProviderEntityId);
            var bindingType = EnumHelper.NumToEnum<Sustainsys.Saml2.WebSso.Saml2BindingType>(identityProvider.Saml2BindingType.Value);

            var idp = new IdentityProvider(idpEntityId, options.SPOptions) {
                MetadataLocation = identityProvider.MetadataLocation,
                LoadMetadata = identityProvider.LoadMetadata,
                AllowUnsolicitedAuthnResponse = identityProvider.AllowUnsolicitedAuthnResponse,
                Binding = bindingType,
            };

            options.IdentityProviders.Add(idp);
            return idp;
        }