Remove the duplcated element and then sort them with Linq

Question

I have an XML file :

  <School>
    <SchoolID>9</SchoolID>
    <SchoolID>3</SchoolID>
    <SchoolID>3</SchoolID>
    <SchoolID>3</SchoolID>
    <SchoolID>4</SchoolID>
    <SchoolID>1</SchoolID>
    <SchoolID>3</SchoolID>
    <SchoolID>9</SchoolID>
    <SchoolID>2</SchoolID>
  </School>

The expecting results should be like:

 <School>
    <SchoolID>1</SchoolID>
    <SchoolID>2</SchoolID>
    <SchoolID>3</SchoolID>
    <SchoolID>4</SchoolID>
    <SchoolID>9</SchoolID>
 </School>

My C# code:

var xdoc = XElement.Load(filePath + "input.xml");
var temp = xdoc.Descendants("SchoolID").OrderBy(x => x.Value).Distinct();
xdoc.Save(filePath + "output_final.xml");

However, the result does not change anything.

My temp value is what I want, how can I update my output xml result?

Many thanks.

DY

You should accept answers to your questions by clicking the hollow check next to your favorite answer for each question. Doing so will give you more reputation. — SLaks, Dec 14 '09 at 18:18

Yuriy Faktorovich · Answer 1 · 2009-12-14T16:05:56.933

2

Your LINQ statement only creates a statement that can be executed later, it doesn't modify anything. The following solves it quickly:

var xdoc = XDocument.Load(filePath + "input.xml");
xdoc.Root.ReplaceAll(xdoc
    .Descendants("SchoolID")
    .DistinctBy(e => e.Value)
    .OrderBy(e => e.Value));
xdoc.Save(filePath + "output_final.xml");

edited Dec 14 '09 at 16:05

answered Dec 14 '09 at 15:48

Yuriy Faktorovich

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Hi Yuriy, thanks very much. Is there any easy way I could get the xml file updated? – Daoming Yang Dec 14 '09 at 15:50
There is no `DistinctBy` method. – SLaks Dec 14 '09 at 16:26
Sorry the DistinctBy came from http://code.google.com/p/morelinq/wiki/OperatorsOverview – Yuriy Faktorovich Dec 14 '09 at 16:29

score 0 · Answer 2 · answered Dec 14 '09 at 15:53

0

Like this:

var ids = xdoc.Descendants("SchoolID")
              .Select(x => int.Parse(x.Value))
              .Distinct()
              .OrderBy(x => x);

var newDoc = new XElement("School", ids.Select(i => new XElement("SchoolID", i));
newDoc.Save(filePath + "output_final.xml");

You ned to call int.Parse to make sure it sorts correctly if an ID is more than 10, and you need to call Select before Distinct because XElement is compared by reference, meaning that no two XElements are equal, even if they have the same content. You could write your own IEqualityComparer, but this way is much easier.

answered Dec 14 '09 at 15:53

SLaks

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1

Maybe reverse the Distinct and OrderBy? – Yuriy Faktorovich Dec 14 '09 at 15:55
Thanks to Intellisense I found DistinctBy. – Yuriy Faktorovich Dec 14 '09 at 16:08
There is no `DistinctBy` method. http://stackoverflow.com/questions/520030/why-is-there-no-linq-method-to-return-distinct-values-by-a-predicate – SLaks Dec 14 '09 at 16:27
Had a feeling it came from MoreLinq/I created it. My fault. – Yuriy Faktorovich Dec 14 '09 at 16:36

score 0 · Answer 3 · answered Dec 14 '09 at 16:51

I got another way to solve this problem by using XSLT.

<xsl:template match="SchoolID">
<xsl:if test="not(node()) or not(preceding-sibling::node()[.=string(current())])">
<SchoolID>
   <xsl:value-of select="SchoolID"/>
</SchoolID>
</xsl:if>   
</xsl:template>

This code dose not include sorting.

Thanks.

DY

Remove the duplcated element and then sort them with Linq

3 Answers3