Get rel value from URL link

Question

I have an xml file that has two links in it. I need to check to see if the link with the rel next exists if it does get the href value of it.

<a:link rel="prev" type="application/atom+xml" type="application/atom+xml" href="/v3.2/en-us/" />
<a:link rel="next" type="application/atom+xml" type="application/atom+xml" href="/v3.2/en-us/" />

Sorry the most i have gotten is string test = ReturnedAppsXml.Element(ns + "link").Attribute(rel).Value; that returns the value of the first link. How other than looping can I check either with regex or what not if the second link exists with the rel value of next — scripter78, Jun 08 '12 at 14:48

score 2 · Accepted Answer · edited Jun 08 '12 at 17:06

2

How about reading the xml into an XDocument and using LINQ to find the next element.

XDocument x = XDocument.Parse("<xml><link rel=\"prev\" type=\"application/atom+xml\" href=\"/v3.2/en-us/\" /> <link rel=\"next\" type=\"application/atom+xml\" href=\"/v3.2/en-us/\" /></xml>");

XElement link = x.Descendants("link")
                 .FirstOrDefault(a => a.Attribute("rel").Value == "next");

String href = string.Empty;
if(link != null)
{
     href = link.Attribute("href").Value; 
}

edited Jun 08 '12 at 17:06

Metro Smurf

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answered Jun 08 '12 at 15:04

Jake1164

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For simplicity I removed the namespace, here is a link to a question about reading xml with namespaces that might come in handy as well. http://stackoverflow.com/questions/8996300/search-xml-element-with-xml-namespace-prefix-c-sharp – Jake1164 Jun 08 '12 at 15:11
This will fail (exception will be thrown) when `.FirstOrDefault` returns the default value of `null` when no value is found for the "rel" attribute. – Metro Smurf Jun 08 '12 at 15:26
Correct, it will throw exceptions if any of the items are missing. I would recommend validating the xml using a schema first. – Jake1164 Jun 08 '12 at 15:34
Even if it validates, the `FirstOrDefault` will cause an exception if the rel attribute (or value) does not exist; there's no requirement that the value must exist. From the OP: _I need to check to see if the link with the rel next exists if it does get the href value of it._ – Metro Smurf Jun 08 '12 at 16:13

score 0 · Answer 2 · answered Jun 08 '12 at 15:30

You can use this public xml library and then get the value with:

XElement root = XElement.Load(file); // or .Parse(string)
string href = root.XGetElement<string>("//a:link[@rel={0}]/href", null, "next");
if(null != href)
    ... link was found ...

That should work with the a:link, but if it doesn't try it without the a:. It would depend on where a's namespace was declared. If it is in the root node it should be fine.

XGetElement() is basically a combination of XPathElement("//a:link[@rel={0}]").Get<string>("href", null). Get() also being a part of the library for getting values from nodes, checking first for an attribute by the name and then for a child node.

Get rel value from URL link

2 Answers2