MainPage.xaml.cs

public partial class MainPage : ContentPage
{
	private MainPage _mainPage;
	public MainPage()
	{
		InitializeComponent();
		_mainPage = this;

		hwebview.Username = "username"; //usually active directory user
		hwebview.Password = "password";
		hwebview.Source = "web_site_proxy_uri";
	}
}