根据地址获取html页面中的内容

        private string GetHtml(string url)
        {
            // 获取文件
            System.Text.Encoding en = System.Text.Encoding.GetEncoding("utf-8");
            var html = "";
            try
            {
                WebClient client = new WebClient();
                client.Encoding = en;
                html = client.DownloadString(url);
            }
            catch (Exception ex)
            {
                html = "err:" + ex.Message + ",地址:" + url;
            }

            return html;
        }