public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
        }

        private void tbWord_TextChanged(object sender, TextChangedEventArgs e)
        {
            IAsyncResult result = this.StartWebRequest("http://en.wikipedia.org/w/api.php?action=opensearch&search=" + tbWord.Text);
            this.FinishWebRequest(result);
        }

        private IAsyncResult StartWebRequest(string url)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            return request.BeginGetResponse(new AsyncCallback(FinishWebRequest), request);
        }

        private void FinishWebRequest(IAsyncResult result)
        {
            HttpWebResponse response = (result.AsyncState as HttpWebRequest).EndGetResponse(result) as HttpWebResponse;
            StreamReader myStreamReader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(1251));
            string data = myStreamReader.ReadToEnd();


        }

    }