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C# code for an Atom reader (advanced C# and sequences)
f#c#deployment

I am processing an atom feed, and found this

excellent code [link:lorgonblog.spaces.live.com].

The F#, as working for my app, is

--------------------------------------------

open System.Xml
open System.ServiceModel.Syndication

let url = "[link:www.redbubble.com]

let AtomFeed

(url : string) =

let reader

= XmlReader.Create(url)

let feed =

SyndicationFeed.Load<SyndicationFeed>(reader)

feed.Items |> Seq.map (fun item ->

item.Links.[1].Uri)

--------------------------------------------

For deployment I am targeting C#, so I translated this to…

public static List<string> GetAtomFeed(string url)

{

List<string>

urls = new List<string>(); XmlReader

reader = XmlReader.Create(url);

SyndicationFeed

feed = SyndicationFeed.Load<SyndicationFeed>(reader);

foreach

(SyndicationItem item in feed.Items)

{

urls.Add(item.Links[1].Uri.ToString());

} return urls;

}

--------------------------------------------

Both are very nice :), but obviously (and unsurprisingly) the F#

is nicest.

For those familiar with current C#, is there a more direct

translation from the F# original? In particularly, can I avoid the "foreach" loop?

.

This should work, assuming feed.Items is strongly typed.

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public static List<string> GetAtomFeed(string url) {
    XmlReader reader = XmlReader.Create(url);
    SyndicationFeed feed = SyndicationFeed.Load<SyndicationFeed>(reader);
    return feed.Items.Select(i => i.Links[1].Uri.ToString()).ToList()
}
By on 4/19/2009 9:55 PM ()

I was hoping that the answer to my question might point me to

something I needed to learn. I've

searched my C# 3 book, and found that Select statement in Linq. So,

looks like I need to work out a bit of Linq, and how that works with

the ServiceModel.SyndicationFeed class.

I'm also curious to find out whether the F# original is using Linq. It's on my to do list, and I'll post back here.

Thanks again, Michael.

By on 4/20/2009 12:37 AM ()

Looking at it like this, LINQ is similar to what is inside the Seq module. Seq.filter = IEnumerable.Where. Seq.map = IEnumerable.Select. And so on. The difference is that C# gets the nice syntax via extension methods instead of pipelines and modules.

By on 4/20/2009 6:39 AM ()

@Michael:

>> Looking at it like this, LINQ is similar to what is inside the Seq

module. Seq.filter = IEnumerable.Where. Seq.map = IEnumerable.Select.

>> And so on. The difference is that C# gets the nice syntax via extension

methods instead of pipelines and modules.

Thanks again Michael.

Inspired by this comparison, I spent an afternoon delving more into Linq, and discovered the joy of chaining the operations.

For my app I had to do a regexp replace on part of the atom feed. With Linq, it turns out very neatly...

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response.photoUrls = 
                feed.Items.Select(item => item.Links[1].Uri.ToString()).
                Select(s => Regex.Replace(s, "size:medium", "size:small")).
                ToList();

The overall solution, with WCF (ServiceModel) and Linq is much better than traditional C#.

I've also done an atom reader in PHP. After looking at the PHP atom "helper" classes, I decided to just use a file read, and sequential string reading and searching!

By on 4/21/2009 8:57 PM ()

Yup! Nice work - thankyou.

>> assuming feed.Items is strongly typed

Yes. In fact, it was very nice using this to process the feed, as I used intellisense to pick the component I needed (item.Links).

By on 4/19/2009 11:11 PM ()

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