What should I return from my service layer? DotNetOpenAuth

I am wondering what should I return in this case. My Ui and service layer 开发者_如何学JAVAare in different projects.

This is what happens

-> User Comes to Site -> User chooses openId provider and hits login -> Post back to controller

 [HttpPost]
        public ActionResult Login(LoginViewModel loginViewModel)
        {
           var test = accountService.SendOpenIdRequest(loginViewModel.OpenId);

        }


public class LoginViewModel
    {
        public OpenId OpenId { get; set; }
    }

So I take in a ViewModel that contains my domain class.

 public class OpenId
    {
        public string Url { get; set; }
    }

So far in my SendOpenIdRequest

  public ?  SendOpenIdRequest(OpenId openId)
        {
            var openIdRelyingParty = new OpenIdRelyingParty();
            var response = openIdRelyingParty.GetResponse();

            Identifier id;
            if (Identifier.TryParse(openId.Url, out id))
            {
                try
                {
                    var req = openIdRelyingParty.CreateRequest(openId.Url);
                    return req.RedirectingResponse
                }
                catch (ProtocolException ex)
                {
                }
            }

            return null;
        }

Now this is where I get lost since their are so many things I could return.

I could return

return req.RedirectingResponse.AsActionResult()

However I think this would be bad as now I am depending on asp.net mvc ActionResult and if I say use this service layer for some other project(maybe I have a webservice that connects to a mobile application). It won't won't work to well.

I could return OutgoingWebResponse but I am not really sure what to do with it once I get it back.

I could also return the IAuthenticationRequest what is generated from CreateRequest()

Finally I could return my Domain Object(OpenId) with one of the ones I listed above in it.

You could return an OutgoingWebResponse:

public OutgoingWebResponse SendOpenIdRequest(OpenId openId)
{
    using (var openIdRelyingParty = new OpenIdRelyingParty())
    {
        var response = openIdRelyingParty.GetResponse();
        Identifier id;
        if (Identifier.TryParse(openId.Url, out id))
        {
            try
            {
                var req = openIdRelyingParty.CreateRequest(openId.Url);
                return req.RedirectingResponse
            }
            catch (ProtocolException ex)
            {
            }
        }
        return null;
    }
}

and then in your controller:

[HttpPost]
public ActionResult Login(LoginViewModel loginViewModel)
{
    var response = accountService.SendOpenIdRequest(loginViewModel.OpenId);
    if (response == null)
    {
        ModelState.AddModelError(
            "openid_identifier", 
            "The specified login identifier is invalid"
        );
        return View();
    }
    return response.AsActionResult();
}