用C# 对页面解析筛选:
var responseHtml = await HttpHelper.GetHtmlStringAsyncByHttpClient(url);
var parser = new HtmlParser();
var document = await parser.ParseDocumentAsync(responseHtml);
var elements = document.QuerySelectorAll("div#three_two_left").Children("div").Where(s => s.Id != "three_col_center");
现在要从elemnts中筛选出所有具有“href”属性的element,应该怎么做?