I have been learning how authorization works in ASP.Net WebApi and I came across an answer by Darin Dimitrov in another posting ( ASP.NET Web API Authentication ) and I need some help understanding why I'm getting a 401.
Following Darin's code, I have created a WebApi project and added the following controllers and model:
AccountController.cs
using System.Web.Http;
using System.Web.Security;
using AuthTest.Models;
namespace AuthTest.Controllers
{
    public class AccountController : ApiController
    {
        public bool Post(LogOnModel model)
        {
            if (model.Username == "john" && model.Password == "secret")
            {
                FormsAuthentication.SetAuthCookie(model.Username, false);
                return true;
            }
            return false;
        }
    }
}
UsersController.cs
using System.Web.Http;
namespace AuthTest.Controllers
{
    [Authorize]
    public class UsersController : ApiController
    {
        public string Get()
        {
            return "This is top secret material that only authorized users can see";
        }
    }
}
LogOnModel.cs
namespace AuthTest.Models
{
    public class LogOnModel
    {
        public string Username { get; set; }
        public string Password { get; set; }
    }
}
I have created a Web Forms app with two buttons and a label for testing purposes.
Default.aspx.cs
using System;
using System.Net.Http;
using System.Threading;
namespace AuthTestWebForms
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }
        protected void ButtonAuthorizeClick(object sender, EventArgs e)
        {
            using (var httpClient = new HttpClient())
            {
                var response = httpClient.PostAsJsonAsync(
                    "http://localhost/authtest/api/account",
                    new { username = "john", password = "secret" },
                    CancellationToken.None
                ).Result;
                response.EnsureSuccessStatusCode();
                bool success = response.Content.ReadAsAsync<bool>().Result;
                if (success)
                {
                    //LabelResponse.Text = @"Credentials provided";
                    var secret = httpClient.GetStringAsync("http://localhost/authtest/api/users");
                    LabelResponse.Text = secret.Result;
                }
                else
                {
                    LabelResponse.Text = @"Sorry, you provided the wrong credentials";
                }
            }
        }
        protected void ButtonTestAuthClick(object sender, EventArgs e)
        {
            using (var httpClient = new HttpClient())
            {
                var secret = httpClient.GetStringAsync("http://localhost/authtest/api/users");
                LabelResponse.Text = secret.Result;
            }
        }
    }
}
When I click the button and run ButtonAuthorizeClick() it fires the controller for Account and then fires the controller for Users and everything is fine.
If I then click the ButtonTestAuthClick(), I get a 401 (Unauthorized) error.
When I look for the ASPXAUTH cookie in Chrome or FireFox, I don't see one, so I'm not 100% sure why ButtonAuthorizeClick() works and what I need to do to make ButtonTestAuthClick() work.
Thanks for any help anybody can throw my way.