How to update XML child node element value in C#?

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I have xml string data and need to update the specific value in that xml return updated xml string.

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
   </book>
   <created>
   <createddate>
   <DateTime>
      2015-05-16T05:50:06.7199222-04:00
   <DateTime>
   <createddate>
   <created>
 <catalog>

I want to update <datetime> with current DateTime.Now

What I have tried:

I have tried with below code.
string xmlData="

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
   </book>
   <created>
   <createddate>
   <DateTime>
      2015-05-16T05:50:06.7199222-04:00
   <DateTime>
   <createddate>
   <created>
 <catalog>

";

;
System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
xmlDoc.LoadXml(xmlData);
xmlDoc.SelectSingleNode("Catalog/Created/createddate/DateTime").InnerText = DateTime.Now;
xmlDoc.Save(xmlData);

but not working could you please assist on this.

Posted 28-Jan-21 1:52am

DGKumar

Updated 28-Jan-21 2:18am

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Comments

Estys 28-Jan-21 8:17am

XML names are case-sensitive, so 'Catalog' != 'catalog'. Your examples suffer from that.

1 solution

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TheRealSteveJudge · Answer 1 · 2021-01-28T02:18:00

Solution 1

First of all you XML is not a valid XML file.
It should look like this

XML

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
   </book>
   <created>
   <createddate>
   <DateTime>
      2015-05-16T05:50:06.7199222-04:00
   </DateTime>
   </createddate>
   </created>
 </catalog>

An open tag must have a close tag.
e.g.

XML

<created></created>

Moreover your SelectSingleNode call does not respect capitalisation.
It must rather be like this:

C#

xmlDoc.SelectSingleNode("catalog/created/createddate/DateTime").InnerText = DateTime.Now.ToString("dd.MM.yyyy");

InnerText is of type string.
Therefore you must convert your DateTime object to a string as it is shown in the example above.

Posted 28-Jan-21 2:18am

TheRealSteveJudge

Comments

DGKumar 28-Jan-21 8:33am

Hi Steve
I have modified with below code
string xmlData = @"<catalog><book><author> Gambardella, Matthew <title> XML Developers Guide<created><createddate><datetime>2015";
System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
xmlDoc.LoadXml(xmlData);
xmlDoc.SelectSingleNode("catalog/created/createddate/DateTime").InnerText = DateTime.Now.ToString("dd.MM.yyyy");
xmlDoc.Save(xmlData);

Now i am getting System.ArgumentException: 'Illegal characters in path.' exception

DGKumar 28-Jan-21 8:38am

Is there any better approach for this ?

TheRealSteveJudge 28-Jan-21 8:55am

Your XML is not valid.
You can store the XML I suggested in a file e.g. input.xml
and load it like this:
var xmlDoc = new XmlDocument();
xmlDoc.Load("input.xml");

Estys 28-Jan-21 9:04am

xmlDoc.Save() expects a filename/path, not an xml-string.

TheRealSteveJudge 28-Jan-21 9:13am

That's right. But the System.ArgumentException already comes when loading the XML.

Estys 28-Jan-21 9:45am

Yes, I suspect he did not post his real code. The error he mentioned ('illegal .. in path') is on the Save.

TheRealSteveJudge 28-Jan-21 10:15am

Maybe.
But
xmlDoc.Load(xmlData)
throws System.ArgumentException: 'Illegal characters in path.'