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Editing a single value in XML file from a windows Form application c#

Posted on 2010-08-19
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Last Modified: 2013-12-17
Hi,

Am using VS2008, I've a c# windows form app and I am loading info from my XML file into various text boxes on the form. (this bit is working) I need to be able to edit one of the text boxes and have this change updated to the XML file. I've had a go at this but, the file doesn't change. (I'm very new to xml, 1 day) My XML file format is similar to the following:


<?xml version="1.0" encoding="utf-8"?>
<Lessons>
  <Lesson ID =" 01">
    <ButtonName>btnLesson01</ButtonName>
    <Title>Lesson One</Title>
    <Description>This will recreate etc etc </Description>
    <Points>1</Points>
  </Lesson>
  <Lesson ID =" 02">
    <ButtonName>btnLesson02</ButtonName>
    <Title>Lesson Two</Title>
    <Description>This will etc etc </Description>
    <Points>9</Points>
  </Lesson>
  <Lesson ID =" 03">
    <ButtonName>btnLesson03</ButtonName>
   <Title>Lesson Three</Title>
    <Description>This will etc etc </Description>
    <Points>4</Points>
  </Lesson>
  <Lesson ID ="04">
    <ButtonName>btnLesson04</ButtonName>
   <Title>Lesson Four</Title>
    <Description>This will etc etc </Description>
    <Points>10</Points>
  </Lesson>
</Lessons>



My attached code isn't updating the Points element though.
lessonID   in   XmlNode nodeToEdit = doc.SelectSingleNode("/Lessons/Lesson[@ID="+lessonID+"]");    is a string which I assign a value to elsewhere.

Any idea? Thanks





XmlReader reader = XmlReader.Create(FILE_NAME);
            XmlDocument doc = new XmlDocument();
            doc.Load(reader);
       
            XmlNode nodeToEdit = doc.SelectSingleNode("/Lessons/Lesson[@ID="+lessonID+"]");
              if (nodeToEdit != null)
              {
                  nodeToEdit["Points"].InnerText = txtPoints.Text;
                  
              }
              doc.Save("FILE_NAME");
              doc = null;

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Question by:gemky
4 Comments
 
LVL 5

Accepted Solution

by:
tvPrasad earned 250 total points
ID: 33477918
Hi,
Are you supplying a valid path file name in save ?
 You should supply path i.e.. C:\Lessons.xml
  doc.Save(@"C:\Lessons.xml");

You can check the xml file for updates once executed.
0
 
LVL 63

Assisted Solution

by:Fernando Soto
Fernando Soto earned 250 total points
ID: 33477976
Hi gemky;

I tested your code without modifying it and it works fine, are you sure it is not updating the correct Lesson ID node, are you looking at the wrong Lesson ID?

Fernando
0
 
LVL 27

Expert Comment

by:nmarun
ID: 33478161
0
 

Author Closing Comment

by:gemky
ID: 33483703
Thanks for your help.   I didn't realise this was actually saving as I was only looking at Lessons.xml in the directory. I hadn't spotted a new file called FILENAME in the directory.

What I was doing was silly, I have

 const string FILE_NAME = "Lessons.xml";

and in the save I had
doc.Save("FILE_NAME");  

doc.Save(FILE_NAME);

Thanks everyone
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