how to modify the encoding of HtmlWeb

I am trying to load a webpage for a windows phone app using the htmlagilitypack, the problem is that the encoding is iso-8859-7 and the htmlWeb class loads the page as a utf. I try to solve this with the following code:

 public auditPage()
        {
            InitializeComponent();
            HtmlWeb hwWeb = new HtmlWeb();
            hwWeb = new HtmlWeb
            {
                AutoDetectEncoding = false,
                OverrideEncoding = Encoding.GetEncoding("iso-8859-7"),
            };
           HtmlWeb.LoadAsync("url", HtmlWeb_load);
        }

But i get the following errors : 'HtmlAgilityPack.HtmlWeb' does not contain a definition for 'OverrideEncoding' 'HtmlAgilityPack.HtmlWeb' does not contain a definition for 'AutoDetectEncoding'. What can i do to encode the html page correctly ?