Produce an RSS Feed Dynamically in IIS

You already have all the pieces you need to actually create the feed: It’s merely an XML file, after all. The more important question is this: When do you generate it?

There are a few options:

• Each time content is created or updated.

• On a regular schedule (once an hour, for example).

• On each request (possibly with caching).

An example of the last option is to create a custom handler for IIS.

In a class library project, define this class:

class RssGenerator : System.Web.IHttpHandler
{
    RssLib.Feed feed = new RssLib.Feed();

    #region IHttpHandler Members

    public bool IsReusable
    {
        get { return true; }
    }

    public void ProcessRequest(System.Web.HttpContext context)
    {
        context.Response.ContentType = "application/xml";
        CreateFeedContent(context.Response.OutputStream);
    }

    #endregion

    private void CreateFeedContent(Stream outStream)
    {
        RssLib.Channel channel = GetFeedFromDB();

        feed.Write(outStream, channel);
    }

    private RssLib.Channel GetFeedFromDB()
    {
        using (IDataReader reader = CreateDataSet().CreateDataReader())
        {
            RssLib.Channel channel = new RssLib.Channel();
            channel.Title = "Test Feed";
            channel.Link = "http://localhost";
            channel.Description = "A sample RSS generator";
            channel.Culture = CultureInfo.CurrentCulture;
            channel.Items = new List<RssLib.Item>();
            while (reader.Read())
            {
                RssLib.Item item = new RssLib.Item();
                item.Title = reader["title"] as string;
                item.Link = reader["link"] as string;
                item.PubDate = reader["pubDate"] as string;
                item.Description = reader["description"] as string;
                channel.Items.Add(item);
            }
            return channel;
        }
    }

    private static DataSet CreateDataSet()
    {
        DataSet dataSet = new DataSet();
        //get results from database and populate DataSet
        return dataSet;
    }
}

					    

To use this in a web project, you must modify the web project’s web.config to reference it:

<httpHandlers>
    ...
    <!-- type="Namespace.ClassName,AssemblyName" -->
    <add verb="GET" path="feed.xml"
         type="IISRssHandler.RssGenerator,IISRssHandler"/>
</httpHandlers>

Now, whenever you access the project’s feed.xml file via a web browser, the handler will intercept the request and run your code to generate the RSS.

Note

Rather than generate the results on each request, you may want to implement a simple caching system—only generate if the results haven’t been generated in the last 10 minutes or so; otherwise, use the previous results.