为什么rxjs epic无法正常工作？

Question

请告诉我是什么问题，操作员zip会遵循条件，但由于输掉比赛，为什么？

        btnRead.Click += (sender, e) =>
        {
            showtxt.Text = ShowRemoteStringFile("ftp://url/text.txt");
        };

    string ShowRemoteStringFile(string readUrl)
    {
        WebRequest req = WebRequest.Create(readUrl);
        req.Credentials = new NetworkCredential("username", "password");
        WebResponse rsp = (WebResponse)req.GetResponse();
        StreamReader rdr = new StreamReader(rsp.GetResponseStream());
        string result = rdr.ReadToEnd();
        return result;
    }