HybridWebView.cs

public class HybridWebView : WebView
{
    public HybridWebView()
    {
    }

    public static readonly BindableProperty UsernameProperty =
        BindableProperty.Create("UserName", typeof(string), typeof(HybridWebView), null, BindingMode.TwoWay);

    public static readonly BindableProperty PasswordProperty =
        BindableProperty.Create("Pwd", typeof(string), typeof(HybridWebView), null, BindingMode.TwoWay);

    public string Username
    {
        get { return GetValue(UsernameProperty).ToString(); }
        set { SetValue(UsernameProperty, value); }
    }

    public string Password
    {
        get { return GetValue(PasswordProperty).ToString(); }
        set { SetValue(PasswordProperty, value); }
    }
}