check if node exists in external rss feed

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Robin Nicholl 137 posts 277 karma points

Jul 23, 2014 @ 19:58
0

Check if node exists in external RSS feed
I'm parsing external RSS feed (for train times); main <Service> nodes sometimes contain <Platform> node and sometimes not. If there is one or more <Service> node without a <Platform> node there is an 'Error loading MacroEngine script' and expected results of macro don't display.
```
<Service Uid="1">
    <DepartTime time="1831" />
    <Destination1 name="Brighton" />
    <Platform Number="9" />
    <ServiceStatus Status="On Time" />
</Service>
<Sefvice Uid="2">
    <DepartTime time="1854" />
    <Destination1 name="Horsham" />
    <ServiceStatus Status="Delayed" />
</Service>
```
How can I check if this node exists so that I don't try displaying non-existent nodes, which makes code fall over?

Thanks

Robin
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Mike Chambers 636 posts 1253 karma points c-trib

Jul 24, 2014 @ 10:16

0

How are you parsing?

You could use the umbraco.library:GetXmlDocumentByUrl('URL') [http://our.umbraco.org/wiki/reference/umbracolibrary/getxmldocumentbyurl]

And once it's xml then use xpath selectsinglenode to determine if the node exists..

alternatively can't you just wrap your try to display the missing node in a try {}catch{} construct...

I guess it all depends on the umbraco version and razor/xslt/usercontrol option that you are using,

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Robin Nicholl 137 posts 277 karma points

Jul 24, 2014 @ 12:58

I have this:

XmlTextReader departuresRSS = new XmlTextReader("path_to_xml");
XmlDocument doc = new XmlDocument();
doc.Load(departuresRSS);
XmlNodeList rssItems = doc.SelectNodes("//Service");
<table>
@{
foreach (XmlNode node in rssItems) {
<tr>
<td>@node["DepartTime"].Attributes["time"].Value</td>
<td>@node["Platform"].Attributes["Number"].Value</td>
</tr>
}
</table>

... but the "Platform" node doesn't always exist (usually, but not always). When it doesn't, the whole thing falls over.

Thanks

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Robin Nicholl 137 posts 277 karma points

Jul 24, 2014 @ 14:27
100
Sorted! This works…
```
var plat = node["Platform"] != null ? node["Platform"].Attributes["Number"].Value : "-";
<td>@plat</td> 
```
Thanks for the pointers, Mike.
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Mike Chambers 636 posts 1253 karma points c-trib

Jul 24, 2014 @ 14:28

0

no worries.. ps the inbuilt library fucntion also accepts a parameter to cache.. in case that appeals (for not have 1000's of users hitting the rss constantly)

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Robin Nicholl 137 posts 277 karma points

Jul 24, 2014 @ 15:35

0

Actually that might be of interest: where would I read up on that?

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Mike Chambers 636 posts 1253 karma points c-trib

Jul 24, 2014 @ 16:27

0

Not sure there is any documentation... I noticed it in the source when I was looking to addess an issue with GetXmlDocumentByUrl() passing a useragent of ie4.. so ending up with issues

https://github.com/umbraco/Umbraco-CMS/blob/d1c5ddc03dfb79195e1c97eededcabc9dcaa1365/src/Umbraco.Web/umbraco.presentation/library.cs

/// <summary>

        /// Gets the XML document by URL Cached.

        /// </summary>

        /// <param name="Url">The URL.</param>

        /// <param name="CacheInSeconds">The cache in seconds (so 900 would be 15 minutes). This is independent of the global cache refreshing, as it doesn't gets flushed on publishing (like the macros do)</param>

        /// <returns></returns>

        public static XPathNodeIterator GetXmlDocumentByUrl(string Url, int CacheInSeconds)

        {

            object urlCache =

                            HttpContext.Current.Cache.Get("GetXmlDoc_" + Url);

            if (urlCache != null)

                return (XPathNodeIterator)urlCache;

            else

            {

                XPathNodeIterator result =

                    GetXmlDocumentByUrl(Url);

                HttpContext.Current.Cache.Insert("GetXmlDoc_" + Url,

                    result, null, DateTime.Now.Add(new TimeSpan(0, 0, CacheInSeconds)), TimeSpan.Zero, System.Web.Caching.CacheItemPriority.Low, null);

                return result;

            }

        }

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