Asp net Core Get user Windows username

Question

Building an intranet in ASP .net CORE mvc, I need to get the Windows username of the current user for the login, I do not need to automaticaly login the user with Windows Authentication, I have already a custom login Controller to do that, I only need his username.
It work fine on local but I cannot get the username when on the IIS server :
Local :

Environment.UserName => VeronY 
System.Security.Principal.WindowsIdentity.GetCurrent().Name => Domain\VeronY

IIS server :

Environment.UserName => Intranet
System.Security.Principal.WindowsIdentity.GetCurrent().Name => APPPOOL\Intranet 

With Windows Auhtentication it auto login me which is not what I need. There must be 2 type of authentication : Automatic with AD and Manual with form manage by Identity Framework.

Answer 1

ASP .net doesn't seem to authorize 2 different types of connection, so I let the main site with form authentication and I 've created a small API :

[Authorize]
[Route("api/[controller]")]
public class ValuesController : Controller
{
    [HttpGet]
    public ActionResult Get()
    {
        return Json(User.Identity.Name);
    }
}

Configure with Windows Authentication.
And here's the LoginController in the main website :

String responseString = "";
        using (var client = new HttpClient())
        {
            client.BaseAddress = new Uri("http://myapiURL");
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            var response = client.GetAsync("api/values").Result;
            if (response.IsSuccessStatusCode)
            {
                responseString = response.Content.ReadAsStringAsync().Result;
                responseString = Regex.Unescape(responseString).Replace("\"","");//Because the response is something like \\"Domaine\\\\Username\"\
            }
            else
            {
                return View();//server cannot be found or Windows authentication fail => form Login
            }
        }
        String username = "";
        String domain = "";

        if (responseString != "" && responseString.Contains("\\"))
        {
            domain = responseString.Split('\\')[0];
            username = responseString.Split("\\")[1];
            if(domain !="MYDOMAIN")
            {
                return View();//Not in the correct domain => form Login
            }
        }
        else
        {
            return View();//Not the correct response => form Login
        }
        UserPrincipal user = UserPrincipal.FindByIdentity(new PrincipalContext(ContextType.Domain), username);


        if (null != user)
        {
            CustomAutomaticLogin(user)//All seems ok, try to log the user with custom login with AD informations
        }
        else
        {
           return View()//Not in AD => form login
        }
}