How to trigger an executable upon update of an RSS feed

I have an RSS feed URL, that I can view in any Feed Reader.

This RSS feed is not controlled by me, it is only consumed by me.

This RSS Feed (Office of Inspector General's Excluded Provider List) links to a page with download-able files.

These files are updated approximately once a month, and the RSS feed displays new "unread" items.

What I want to do is write something (in C#) that checks this RSS Feed once a week, and when a new item (i.e. a new download-able file) is available, triggers off an executable.

This is essentially like a very scaled-down RSS Reader, with the sole purpose of triggering an executable when a new item appears.

Any guidance, advice would be greatly appreciated.

Edit:

• I 开发者_开发百科need help in determining when a new item becomes available for download.
• The running of an executable I can do.
• The executable that will run, will process the downloaded file.

As a commenter already noted, this question is quite broad, but here's an attempt to answer:

• You can either write a Windows Service (use a template that comes with VS/MonoDevelop) or you can write a simple console app that would be called by Windows Scheduler or Cron.

• The main code will use one of the many RSS feed parsers available:

There are plenty of examples here on SO. IMO, the simplest LINQ-based is here

I personally like this approach, also using LINQ.

• Once you parse the feed, you need to look for the value of the Link element, found by doing this from the SO example above:

....

var feeds = from feed in feedXML.Descendants("item")
              select new
              {
                Title = feed.Element("title").Value,
                **Link** = feed.Element("link").Value,
                Description = feed.Element("description").Value
              };

....

• So, now that you have the executable, you'll need to download it to your machine. I suggest you look into this example from MSDN:
• Now, that you have the file downloaded, simple use Process.Start("Path to EXE"); to execute it.

Watch out for viruses in the exes!!!

If you are using .Net 3.5 or above you can you the various classes within the System.ServiceModel.Syndication namespace, specifically the SyndicationFeed class which exposes a LastUpdatedTime property that you can use to compare dates to know when to call your executable using the Process.Start method in the System.Diagnostics namespace.

            using (XmlReader reader = XmlReader.Create(path))
            {
                SyndicationFeed feed = SyndicationFeed.Load(reader);

                if ((feed != null) && (feed.LastUpdateTime > feedLastUpdated))
                {
                    // Launch Process                            
                }
            }

So you have to read the RSS feed from the URL, and then parse the data to determine whether a new item is available.

To read the feed, you'll want to use a WebClient. The simplest way:

var MyClient = new WebClient();
string rssData = MyClient.DownloadString("http://whatever");

You can then create an XML document from the returned string.

var feedXML = new XMlDocument();
feedXML.Load(rssData);

@dawebber shows how to parse the XML with LINQ. You'll want to check the date on each item to see if it's newer than the last date checked. Or perhaps you have a database of items that you've already seen and you want to check to see if the items you received are in the database.

Whenever you find a new item, you can fire off your executable using Process.Start.

You could write a System Tray application. I've done several that screen scrape/monitor sites on a scheduled basis. Here is a VERY simple start. I think you could do what you're looking for in a few hours.

http://alperguc.blogspot.com/2008/11/c-system-tray-minimize-to-tray-with.html