Updating XML element using C#

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Hi again,
now I'm using the XDocument class:

C#

        XDocument doc2 = XDocument.Parse(@"
    <kml xmlns='http://www.opengis.net/kml/2.2' xmlns:gx='http://www.google.com/kml/ext/2.2' xmlns:kml='http://www.opengis.net/kml/2.2' xmlns:atom='http://www.w3.org/2005/Atom'>
        <Placemark>
             <name>Test</name>
             <LookAt>
            <longitude>11111111111</longitude>
            <latitude>1111111111111</latitude>
            <altitude>500</altitude>
            <range>500</range>
            <tilt></tilt>
            <heading>11111111</heading>
            <altitudeMode>relativeToGround</altitudeMode>
           </LookAt>
          <styleUrl>#msn_ylw-pushpin70</styleUrl>
          <Point>
            <coordinates>111111111,1111111111</coordinates>
          </Point>
      </Placemark>
</kml>");

So as I mentioned before that I need to update the "longitude" element content so I used;

C#

doc2.Element("kml").Element("longitude").Value = "XXXXX";

I get now the exception "Object reference not set to an instance of an object"
I know that there is a problem reaching the "longitude" element so what is the method which enables me to do it, because I tried many times and searched alot..

Many thanks.

Posted 16-Nov-12 23:40pm

M.S.S.E

Updated 17-Nov-12 23:44pm

v4

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OriginalGriff · Answer 1 · 2012-11-16T23:47:00

We do not do your homework: it is set for a reason. It is there so that you think about what you have been told, and try to understand it. It is also there so that your tutor can identify areas where you are weak, and focus more attention on remedial action.

Try it yourself, you may find it is not as difficult as you think!

There are a lot of examples out there, that just need you to tweek them to your specific needs. Asking for "I need the full code starting from loading the file and finishing with saving and closing it." is not trying to do it and failing, it's purely trying to get us to do it for you because you can't be bothered, and that helps nobody in the long term.

Dominic Abraham · Answer 2 · 2012-11-17T00:35:00

Hi
You can find many good articles in internet describing how to read/traverse/update xml.
You can use LINQ to XML mechanism.

http://msdn.microsoft.com/en-us/library/bb387098.aspx

LINQ to XML[^]

Or you can simply
1. Read the xml file in to dataset
2. Modify the dataset
3. Update back in to xml.
For Ex:

C#

    DataSet oDs = new DataSet();
oDs.ReadXml("D:\\yourfile.xml");
if (oDs != null && oDs.Tables.Count > 0 && oDs.Tables[0].Rows.Count > 0  && oDs.Tables[1].Rows.Count > 0)
{
    for (int i = 0; i < oDs.Tables[0].Rows.Count; i++)
    {
        oDs.Tables[0].Rows[i]["name"] = "newName";
        oDs.Tables[0].Rows[i]["PlaceMark_ID"] = "newID";
    }
    for (int i = 0; i < oDs.Tables[1].Rows.Count; i++)
    {
        oDs.Tables[0].Rows[i]["lnngtitude"] = "newval";
    }
}
oDs.AcceptChanges();
oDs.WriteXml("D:\\yourfile.xml");

This may not be the best solution. Try to understand various mechanisms. And have a good idea about this. You just try what you know. And if you found any errors, just post here other than expecting the full source code. All the best

Vivek Krishnamurthy · Answer 3 · 2012-11-17T01:08:00

Solution 3

I completely agree with OriginalGriff. I would say it would have been better if you post the problem you faced.

You can take a look at the following link, it provides one of the many ways to update an xml document.

LINQ to XML Update Element Values[^]

Posted 17-Nov-12 1:08am

Vivek Krishnamurthy

M.S.S.E · Answer 4 · 2012-11-18T21:02:00

Thanx for kuthuparakkal http://www.codeproject.com/Members/kuthuparakkal

C#

using System.Xml.Linq;
using System.Xml;
using System.Xml.XPath;
 
XDocument doc2 = XDocument.Parse(@"
    		<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom">
                <placemark>
		             <name>Test</name>
			         <lookat>
				    <longitude>11111111111</longitude>
				    <latitude>1111111111111</latitude>
				    <altitude>500</altitude>
				    <range>500</range>
				    <tilt></tilt>
				    <heading>11111111</heading>
				    <altitudemode>relativeToGround</altitudemode>
			       </lookat>
			      <styleurl>#msn_ylw-pushpin70</styleurl>
			      <point>
				    <coordinates>111111111,1111111111</coordinates>
			      </point>
              </placemark>
        </kml>");
 
XmlNamespaceManager xnm = new XmlNamespaceManager(new NameTable()); 
xnm.AddNamespace("x", "http://www.opengis.net/kml/2.2");
 
var longitude = doc2.XPathSelectElement("//x:longitude", xnm);
//var longitude = doc2.XPathSelectElement("/x:kml/x:Placemark/x:LookAt/x:longitude", xnm); this also works!
longitude.Value = "XXXXX";

Updating XML element using C#

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