How to Update a XML Node?

Question

It is easy to read an XML file and get the exact Node Text, but how do I Update that Node with a new value?

To read:

public static String GetSettings(SettingsType type, SectionType section)
{
    XmlTextReader reader = new XmlTextReader(HttpContext.Current.Request.MapPath(APPSETTINGSPATH));
    XmlDocument document = new XmlDocument();
    document.Load(reader);

    XmlNode node = document.SelectSingleNode(
                        String.Format("/MyRootName/MySubNode/{0}/{1}",
                        Enum.Parse(typeof(SettingsType), type.ToString()),
                        Enum.Parse(typeof(SectionType), section.ToString())));       
    return node.InnerText;
}

to write ...?

public static void SetSettings(SettingsType type, SectionType section, String value)
{
    try
    {
        XmlTextReader reader = new XmlTextReader(HttpContext.Current.Request.MapPath(APPSETTINGSPATH));
        XmlDocument document = new XmlDocument();
        document.Load(reader);

        XmlNode node = document.SelectSingleNode(
                            String.Format("/MyRootName/MySubNode/{0}/{1}",
                            Enum.Parse(typeof(SettingsType), type.ToString()),
                            Enum.Parse(typeof(SectionType), section.ToString())));
        node.InnerText = value;
        node.Update();
    }
    catch (Exception ex)
    {
        throw new Exception("Error:", ex);
    }
}

Note the line, node.Update(); does not exist, but that's what I wanted :)

I saw the XmlTextWriter object, but it will write the entire XML to a new file, and I just need to update one value in the original Node, I can save as a new file and then rename the new file into the original name but... it has to be simpler to do this right?

Any of you guys have a sample code on about to do this?

Thank you

Answer 1

XmlDocument.Load has an overload that will take the filename directly so there is no need for the reader.

Similarly when you are done XmlDocument.Save will take a filename to which it will save the document.

Answer 2

You don't need an "update" method - setting the InnerText property updates it. However, it only applies the update in memory. You do need to rewrite the whole file though - you can't just update a small part of it (at least, not without a lot of work and no out-of-the-box support).

Answer 3

You're updating the node in an in-memory representation of the xml document, AFAIK there's no way to update the node directly in the physical file. You have to dump it all back to a file.

Answer 4

The nodeValue property can be used to change the value of a text node.

The following code changes the text node value of the first element: Example: xmlDoc=loadXMLDoc("books.xml");

x=xmlDoc.getElementsByTagName("title")[0].childNodes[0]; x.nodeValue="Easy Cooking";

source: http://www.w3schools.com/DOM/dom_nodes_set.asp