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<meta content="text/html;charset=utf-8">					

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        /// <summary>
        /// Konvertiert die Umlaute usw.
        /// </summary>
        /// <param name="text"></param>
        /// <returns></returns>
        private string convertText2Unicode(string text)
        {
            if (text.Contains("%3A"))
                text = text.Replace("%3A", ":");

            if (text.Contains("%27"))
                text = text.Replace("%27", "'");

            if (text.Contains("ß"))
                text = text.Replace("ß", "ß");

            if (text.Contains("ä"))
                text = text.Replace("ä", "ä");

            if (text.Contains("ö"))
                text = text.Replace("ö", "ö");

            if (text.Contains("ü"))
                text = text.Replace("ü", "ü");

            if (text.Contains("Ä"))
                text = text.Replace("Ä", "Ä");

            if (text.Contains("Ö"))
                text = text.Replace("Ö", "Ö");

            if (text.Contains("Ãœ"))
                text = text.Replace("Ãœ", "Ü");

            // € Zeichen entfernen
            if (text.Contains("€"))
                text = text.Replace(" €", "");

            return text;
        }					

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        private void btnStart_Click(object sender, EventArgs e)
        {
            string strUtf8 = "ä";
            MessageBox.Show(DecodeFromUtf8(strUtf8));
        }

        public static string DecodeFromUtf8(string utf8String)
        {
            // copy the string as UTF-8 bytes.
            byte[] utf8Bytes = new byte[utf8String.Length];
            for (int i = 0; i < utf8String.Length; ++i)
            {
                //Debug.Assert( 0 <= utf8String[i] && utf8String[i] <= 255, "the char must be in byte's range");
                utf8Bytes[i] = (byte)utf8String[i];
            }

            return Encoding.UTF8.GetString(utf8Bytes, 0, utf8Bytes.Length);
        }					

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HttpWebRequest request = (HttpWebRequest)WebRequest.Create(strUrl);
request.Proxy = null;
request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:29.0) Gecko/20100101 Firefox/29.0";

var response = request.GetResponse();
var responseStream = response.GetResponseStream();
var doc = new HtmlAgilityPack.HtmlDocument();
doc.Load(responseStream);

// Jetzt wird sich durch die Datei gehangelt und der gesuchte Text in einem normalen String gespeichert.