【建站系列】 Blogroll

Blogroll为站点提供新闻聚合功能，根据RssUrl自动读取RssFeeds.
鉴于rss标准虽然早已成型，但大部分站点都没有遵守rss标准规范，因此在编写blogroll功能时，我仅获取rss的必需属性: title, link, pubDate!

类关系图：

RssItem: Rss元素对象，主要包括标题，链接，作者，发布日期等信息。
Blogroll: 由RssUrl获取RssItem并生成Blogroll的操作类。

代码：

1. RssItem

1 /// <summary>
2 /// Rss Item Instance
3 /// </summary>
4 public class RssItem
5 {
6     /// <summary>
7     /// Create a new <see cref="BlogRoll.API.RssItem"/> instance with no parameters
8     /// </summary>
9     public RssItem() { }
10     /// <summary>
11     /// Title of RssItem
12     /// </summary>
13     public string Title { get; set; }
14     /// <summary>
15     /// Author of RssItem
16     /// </summary>
17     public string Author { get; set; }
18     /// <summary>
19     /// Link of RssItem
20     /// </summary>
21     public string Link { get; set; }
22     /// <summary>
23     /// Publish date of RssItem
24     /// </summary>
25     public DateTime PubDate { get; set; }
26 }

2. Blogroll

1 /// <summary>
2 /// Bllogroll class
3 /// </summary>
4 public sealed class Blogroll
5 {
6     /// <summary>
7     /// Load rss items from the url of rss feed
8     /// </summary>
9     /// <param name="RssUrl">rss url</param>
10     /// <param name="num">numbers</param>
11     /// <returns></returns>
12     public static List<RssItem> LoadRssItems(string RssUrl, int num)
13     {
14         List<RssItem> items = new List<RssItem>();
15         WebClient wc = new WebClient();
16         wc.Encoding = Encoding.UTF8;
17         XElement xe = null;
18         using (Stream stream = wc.OpenRead(RssUrl))
19         {
20             XmlTextReader xmlReader = new XmlTextReader(stream);
21
22             xe = XElement.Load(xmlReader);
23         }
24
25         var query = (
26                             from q in xe.Element("channel").Elements("item")
27                             orderby DateTime.Parse(q.Element("pubDate").Value) descending
28                             select new RssItem
29                             {
30                                 Title = q.Element("title").Value,
31                                 Link = q.Element("link").Value,
32                                 PubDate = DateTime.Parse(q.Element("pubDate").Value)
33                             }).Take(num);
34
35         return query.ToList();
36     }
37 }