SAMLController3.cs

private const string ssoPendingSessionKey = "ssoPending";
private const string ssoSPSessionKey = "partnerSP";

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;
	string partnerSP = null;
	
    if (!(ssoPending && User.Identity.IsAuthenticated)) {
		
        // 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();
        }
    }
	
	// Clear pending here..
	Session[ssoPendingSessionKey] = null; 
	
	// Check/respond to SSO
	return RedirectToAction("SSOService2", "SAMLController",
		new
		{
			partnerSP = partnerSP
		});   
}

public ActionResult SSOService2(string partnerSP) {  
 
	if (!Allowed(partnerSP))
	{			
		// Ask user to approve and return back
		return RedirectToAction("Index", "Approve",
			new
			{
				returnUrl = "/saml/ssoservice2?partnerSP=" + HttpUtility.UrlEncode(partnerSP) 
			});
	}
	
    // 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 = GetUsername();
	
    // Get partner SP attributes, this uses the attribute names the SP expects
    IDictionary<string, string> attributes = GetAttributes(partnerSP);   

    SAMLIdentityProvider.SendSSO(Response, userName, attributes);

    return new EmptyResult();
}