XML - help with RSS UTF-8 support

I used this solution to read and parse a RSS feed from an ASP.NET website. This worked perfectly. However, when trying it on another site, an error occurs because "System does not support 'utf8' encoding." Below I have included an extract of my code.

    private void Form1_Load(object sender, EventArgs e)
    {
        lblFeed.Text = ProcessRSS("http://buypoe.co开发者_开发技巧m/external.php?type=RSS2", "ScottGq");

    }

    public static string ProcessRSS(string rssURL, string feed)
    {
        WebRequest request = WebRequest.Create(rssURL);
        WebResponse response = request.GetResponse();
        StringBuilder sb = new StringBuilder("");
        Stream rssStream = response.GetResponseStream();
        XmlDocument rssDoc = new XmlDocument();
        rssDoc.Load(rssStream);
        XmlNodeList rssItems = rssDoc.SelectNodes("rss/channel/item");
        string title = "";
        string link = "";
   ...

The error occurs at "rssDoc.Load(rssStream);". Any help in encoding the xml correctly would be appreciated.

---

use the following code for encoding

 System.IO.StreamReader stream = new System.IO.StreamReader
                    (response.GetResponseStream(), System.Text.Encoding.GetEncoding("utf-8"));