SAMLController1.cs

private const string ssoPendingSessionKey = "ssoPending";

public ActionResult SSOService() {
    // Either an authn request has been received or login has just completed in response to a previous authn request.
    // The SSO pending session flag is false if an authn request is expected. Otherwise, it is true if
    // a login has just completed and control is being returned to this page.
    bool ssoPending = Session[ssoPendingSessionKey] != null && (bool)Session[ssoPendingSessionKey] == true;

    if (!(ssoPending && User.Identity.IsAuthenticated)) {
        string partnerSP = null;

        // Receive the authn request from the service provider (SP-initiated SSO).
        SAMLIdentityProvider.ReceiveSSO(Request, out partnerSP);

        // If the user isn't logged in at the identity provider, force the user to login.
        if (!User.Identity.IsAuthenticated) {
            Session[ssoPendingSessionKey] = true;
            FormsAuthentication.RedirectToLoginPage();
            return new EmptyResult();
        }
    }

    Session[ssoPendingSessionKey] = null;

    // The user is logged in at the identity provider.
    // Respond to the authn request by sending a SAML response containing a SAML assertion to the SP.
    // Use the configured or logged in user name as the user name to send to the service provider (SP).
    // Include some user attributes.
    string userName = WebConfigurationManager.AppSettings[AppSettings.SubjectName];

    if (string.IsNullOrEmpty(userName)) {
        userName = User.Identity.Name;
    }

    IDictionary<string, string> attributes = new Dictionary<string, string>();

    foreach (string key in WebConfigurationManager.AppSettings.Keys) {
        if (key.StartsWith(AppSettings.Attribute)) {
            attributes[key.Substring(AppSettings.Attribute.Length + 1)] = WebConfigurationManager.AppSettings[key];
        }
    }

    SAMLIdentityProvider.SendSSO(Response, userName, attributes);

    return new EmptyResult();
}