There's already quite a comprehensive RSS tool on The Code Project: RSS 2.0 Framework written by "Jerry Maguire". The purpose of this,
RssReader class, is to provide a simple tool for retrieving RSS feeds from remote and local sources, without needing to parse XML in each application you require the RSS feed in. The class, as its name suggests, only reads RSS feeds - it has no capabilities for writing feeds.
The RSS Format
The RSS (Really Simple Syndication) specification is found at http://blogs.law.harvard.edu/tech/rss. It's an XML format for retrieving, typically, headlines or the latest article details from other sites. For example, the New York Times provide an RSS feed of their main headlines, which you can access and put inside your own site or application.
The RSS format is true to its name - simple. As the image below shows, it contains a root RSS node, which has a channel node beneath it. Inside this channel node, there are a number of elements to describe the feed. Then, after these is a list of articles, headlines, stories or whatever they contain in the form of item nodes. Each item node contains elements to describe themselves - title, description and link are the 3 required elements, there are other optional ones which you can read about in the specification and the
RssReader class docs.
RssFeed and RssItem Objects
Given the simplicity of the RSS format, it was straightforward to map its structure to a value type (
struct).The image below shows the
In this are most (some haven't been implemented in this version) of the fields that RSS offers. There is an
Items property, which contains a collection of
RssItem objects. The
RssItem type maps to an
RSS item, containing most of the fields available to an
RssReader class has one main method,
RetrieveFeed which returns an
RssFeed object, given a URL. This URL can be in the format of file:// as well as the standard http://, if you want to open a local file (it's not been tried with ftp://).
I added several
static methods to make the process even simpler, they're all self explanatory. Also included in the class library is a class called
RssHtmlMaker. This is a simple tool I wrote to turn a
RssFeed object into an HTML (or any other format) document, given a template containing tokens. These tokensmap to the RSS fields available. Details of the tokens are in the documentation.
Included in the
RssReader is the ability to read simple RDF format feeds. RDF (Resource Description Framework) is an W3C XML format for describing web resources. The format caters for describing the content of the web resource, including items such as title, description and URL. There were a couple of RDF feeds which I wanted to use, specifically the slashdot.org feed and the register.com feed. The main way these RDF documents differ
from their RSS counter-parts is the
<items> nodes are children of the main root RSS (or in this case rdf) node, rather than the
<channel> node.. This is catered for in the
RssReader class via the member variable
RdfMode, which is set to
false by default. The RDF specification is found at http://www.w3.org/TR/2004/REC-rdf-primer-20040210/.
One final thing to note: to save yourself at worst being ip-banned by the hosts of the feeds, and at best just upsetting the feed providers, I'd recommend caching the feeds once you get them, rather than retrieving the feed each time it's required. This can be done by serializing the
RssFeed class, or creating an HTML version of the feed and saving it to disk.
Hopefully, the class is useful to people - I've not managed to find any C# RSS Feeds about, if there are any, then leave a URL below.
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London based C# programmer.
I maintain my own pet C# site http://www.sloppycode.net in my spare time.