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

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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gemkyAsked:
Who is Participating?
 
tvPrasadConnect With a Mentor Commented:
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.
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Fernando SotoConnect With a Mentor RetiredCommented:
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
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nmarunCommented:
0
 
gemkyAuthor Commented:
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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