c# - 如何使用 LINQ to XML 从两个 Atom 提要创建聚合 Atom 提要

Question

刚刚尝试创建一个聚合提要 - 来自两个独立的 Atom 提要 - 按发布日期降序排列...

更新:感谢 Martin Honnen(MVP)在 http://social.msdn.microsoft.com/Forums/en-US/categories/ - 结合安全的 XElement.Load(url) 帮助程序(和迭代器 block )...我认为下面的代码是聚合 Xml 文档的一种非常好的方法(在这种情况下聚合站点地图 - 尽管这可以很容易地适应 Atom 或RSS 提要)。

下面的命名空间转换助手只转换元素而不转换属性(尽管也可以添加)。

static void Main(string[] args)
{
    XDocument feed = MergeSiteMaps(new List<string>() { "http://www.58bits.com/blog/googleSitemap.ashx", "http://www.58bits.com/otherblog/googleSiteMap.ashx",  "http://www.58bits.com/photos/sitemap.xml"});

    XNamespace sm = "http://www.sitemaps.org/schemas/sitemap/0.9";

    foreach (XElement location in feed.Root.Elements(sm + "url").Elements(sm + "loc")) 
    {
        Console.WriteLine((string)location); 
    } 
}

public static XDocument MergeSiteMaps(IEnumerable<string> urls)
{
    XNamespace sm = "http://www.sitemaps.org/schemas/sitemap/0.9";
    XNamespace xsi = "http://www.w3.org/2001/XMLSchema-instance";
    XNamespace xsd = "http://www.w3.org/2001/XMLSchema";
    string schemaLocation = "http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd";

    //Our container sitemap document
    return new XDocument(
        new XDeclaration("1.0", "utf-8", "yes"),
        new XElement(sm + "urlset",
            new XAttribute(XNamespace.Xmlns + "xsi", xsi),
            new XAttribute(XNamespace.Xmlns + "xsd", xsd),
            new XAttribute(xsi + "schemaLocation", schemaLocation),

            new XElement(sm + "url",
                new XElement(sm + "loc", "http://www.58bits.com/"),
                new XElement(sm + "lastmod", DateTime.Now.ToString("yyyy-MM-dd")),
                new XElement(sm + "changefreq", "monthly"),
                new XElement(sm + "priority", "1.0")),

            new XElement(sm + "url",
               new XElement(sm + "loc", "http://www.58bits.com/default.aspx"),
               new XElement(sm + "lastmod", DateTime.Now.ToString("yyyy-MM-dd")),
               new XElement(sm + "changefreq", "monthly"),
               new XElement(sm + "priority", "1.0")),

            GetElements(sm, urls, "url"))
        );
}

private static IEnumerable<XElement> GetElements(XNamespace ns, IEnumerable<string> urls, string elementLocalName)
{
    XElement source;

    foreach (string url in urls)
    {
        try
        {
            source = XElement.Load(url);
        }
        catch (Exception ex)
        {
            //TODO: Log the Url that failed
            string message = ex.Message;
            continue;
        }

        XNamespace defaultNamespace = source.GetDefaultNamespace();
        bool differentNamespace = (ns != defaultNamespace);
        foreach (XElement element in source.Elements(defaultNamespace + elementLocalName))
        {
            if (differentNamespace)
                ChangeNamespace(ns, element);
            yield return element;
        }
    }
}

private static void ChangeNamespace(XNamespace ns, XElement entry)
{
    foreach (XElement e in entry.DescendantsAndSelf())
    {
        if (e.Name.Namespace != XNamespace.None)
        {
            e.Name = ns.GetName(e.Name.LocalName);
        }
    }
}

Answer 1

我会查看 SyndicationFeed类(class)。下面是使用它生成提要的示例。

private static SyndicationFeed CreateFeed(List<SyndicationItem> items)
{
    // Create the list of syndication items. These correspond to Atom entries
    SyndicationFeed feed;

    // create the feed containing the syndication items.
    feed = new SyndicationFeed()
    {
        // The feed must have a unique stable URI id
        Id = "http://example.com/MyFeed",
        Title = new TextSyndicationContent("My Feed"),
        Items = items
    };
    feed.AddSelfLink(WebOperationContext.Current.IncomingRequest.GetRequestUri());
    return feed;
}

private static SyndicationItem CreateItem()
{
    var item = new SyndicationItem()
       {
           // Every entry must have a stable unique URI id
           Id = id.ToString(),
           Title = new TextSyndicationContent(title),
           // Every entry should include the last time it was updated
           LastUpdatedTime = startDate,
           // The Atom spec requires an author for every entry. If the entry has no author, use the empty string
           Authors = 
               { 
                   new SyndicationPerson() 
                       {
                           Name = author.Name,
                           Email = author.EmailAddress,
                           Uri = author.Website
                       }
               },
           // The content of an Atom entry can be text, xml, a link or arbitrary content. In this sample text content is used.
           Content = new TextSyndicationContent(description),
       };

    return item;
}