I can't put the result of the JSON response in an object

Question

I am using a PHP API to return the data of a user and i am trying to get the result into an object.When i try to put it in a user object it just throws an exception at runtime.This is a WPF program that i was trying to get user data , which consists of username and password and a boolean which states if he logged in or not.

namespace WpfApp3 {
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow: Window {
    public MainWindow() {
        InitializeComponent();
    }

    private async void show_selection(object sender, RoutedEventArgs e) {
        var userName = username.Text;
        var passWord = password.Text;
        var formContent = new FormUrlEncodedContent(new [] {
            new KeyValuePair < string, string > ("username", userName),
                new KeyValuePair < string, string > ("password", passWord)
        });

        var client = new HttpClient();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        client.BaseAddress = new Uri("http://localhost/pharmasuite/login1.php");
        var response = await client.PostAsync(client.BaseAddress.ToString(), formContent);

        var user = await response.Content.ReadAsAsync < user > ();
        if (user.logged_in == true) {

            MessageBox.Show("logged in");
        }

    }

    class user {
        public string username {
            get;
            set;
        }
        public string password {
            get;
            set;
        }
        public bool logged_in {
            get;
            set;
        }

    }

}