FeedParser.cs

using System;
using System.Globalization;
using System.Collections.Generic;
using System.Linq;
using System.Xml.XPath;
using System.Xml.Linq;

namespace CLReader
{
	/// <summary>
	/// A simple RSS, RDF and ATOM feed parser.
	/// </summary>
	public class FeedParser
	{
		/// <summary>
		/// Parses the given <see cref="FeedType"/> and returns a <see cref="IList&amp;lt;Item&amp;gt;"/>.
		/// </summary>
		/// <returns></returns>
		public IList<Item> Parse(string url, FeedType feedType)
		{
			switch (feedType)
			{
				case FeedType.RSS:
					return ParseRss(url);
				case FeedType.RDF:
					return ParseRdf(url);
				case FeedType.Atom:
					return ParseAtom(url);
				default:
					throw new NotSupportedException(string.Format("{0} is not supported", feedType.ToString()));
			}
		}

		/// <summary>
		/// Parses an Atom feed and returns a <see cref="IList&amp;lt;Item&amp;gt;"/>.
		/// </summary>
		public virtual IList<Item> ParseAtom(string url)
		{
			try
			{
				XDocument doc = XDocument.Load(url);
				// Feed/Entry
				var entries = from item in doc.Root.Elements().Where(i => i.Name.LocalName == "entry")
							select new Item
							{
								FeedType = FeedType.Atom,
								Content = item.Elements().First(i => i.Name.LocalName == "content").Value,
								Link = item.Elements().First(i => i.Name.LocalName == "link").Attribute("href").Value,
								PublishDate = ParseDate(item.Elements().First(i => i.Name.LocalName == "published").Value),
								Title = System.Net.WebUtility.HtmlDecode(item.Elements().First(i => i.Name.LocalName == "title").Value)
							};
				return entries.ToList();
			}
			catch
			{
				return new List<Item>();
			}
		}

		/// <summary>
		/// Parses an RSS feed and returns a <see cref="IList&amp;lt;Item&amp;gt;"/>.
		/// </summary>
		public virtual IList<Item> ParseRss(string url)
		{
			try
			{
				XDocument doc = XDocument.Load(url);
				// RSS/Channel/item
				var entries = from item in doc.Root.Descendants().First(i => i.Name.LocalName == "channel").Elements().Where(i => i.Name.LocalName == "item")
							select new Item
							{
								FeedType = FeedType.RSS,
								Content = item.Elements().First(i => i.Name.LocalName == "description").Value,
								Link = item.Elements().First(i => i.Name.LocalName == "link").Value,
								PublishDate = ParseDate(item.Elements().First(i => i.Name.LocalName == "pubDate").Value),
								Title = System.Net.WebUtility.HtmlDecode(item.Elements().First(i => i.Name.LocalName == "title").Value)
							};
				return entries.ToList();
			}
			catch
			{
				return new List<Item>();
			}
		}

		/// <summary>
		/// Parses an RDF feed and returns a <see cref="IList&amp;lt;Item&amp;gt;"/>.
		/// </summary>
		public virtual IList<Item> ParseRdf(string url)
		{
			try
			{
				XDocument doc = XDocument.Load(url);
				// <item> is under the root
				var entries = from item in doc.Root.Descendants().Where(i => i.Name.LocalName == "item")
							select new Item
							{
								FeedType = FeedType.RDF,
								Content = item.Elements().First(i => i.Name.LocalName == "description").Value,
								Link = item.Elements().First(i => i.Name.LocalName == "link").Value,
								PublishDate = ParseDate(item.Elements().First(i => i.Name.LocalName == "date").Value),
								Title = System.Net.WebUtility.HtmlDecode(item.Elements().First(i => i.Name.LocalName == "title").Value)
							};

				return entries.ToList();
			}
			catch
			{
				return new List<Item>();
			}
		}

		private DateTime ParseDate(string dateString)
		{
			DateTime result;

			//Console.WriteLine($"Date String: {dateString}");

            if (DateTime.TryParse(dateString, out result))
			{
				//Console.WriteLine($"result1: {result}");
				return result;
			}
			else
			{
				if (DateTime.TryParseExact(dateString, "ddd, dd MMM yyyy HH:mm:ss 'GMT'K", CultureInfo.InvariantCulture, DateTimeStyles.None, out result))
				{
					//Console.WriteLine($"result2: {result}");
					return result;
				}
				else
				{
					//Console.WriteLine($"min value");
					return DateTime.MinValue;
				}
			}
		}
	}
	/// <summary>
	/// Represents the XML format of a feed.
	/// </summary>
	public enum FeedType
	{
		/// <summary>
		/// Really Simple Syndication format.
		/// </summary>
		RSS,
		/// <summary>
		/// RDF site summary format.
		/// </summary>
		RDF,
		/// <summary>
		/// Atom Syndication format.
		/// </summary>
		Atom
	}
}