C# Add element to existing XML

Question

Answers to similar questions aren't helping me; or I'm missing something very obvious.

I want to add a <value> element into a <question> element in XML structured like this:

<form>
    <foo>
        <bar>
            <question id="1">...</question>
            <question id="2">...</question>
        </bar>
    </foo>
</form>

Other questions seem to focus on adding an element into the root element but I'm trying to add mine further into the tree based on attribute values. I have tried the following which doesn't work:

XDocument newFormTemplateXML = XDocument.Load("newFormTemplate.xml");
XElement newValue = new XElement("value", 123);
newFormTemplateXML
    .Descendants()
    .Where(d => d.Name.ToString().Equals("question") && d.Attribute("id").Equals(1))
    .Append(newValue);
newFormTemplateXML.Save("test.xml");

I'm not getting an error message. Can someone help me on the right path please?

Try to use "Add" instead of "Append". By the way is newValue element inserted somewhere? — Brank Victoria
– Brank Victoria, Commented Oct 29, 2018 at 12:20
Also, take a look to this social.msdn.microsoft.com/Forums/vstudio/en-US/… — Brank Victoria
– Brank Victoria, Commented Oct 29, 2018 at 12:25
I've tried Add() to no avail - except for adding newValue to the root with newFormTemplateXML.Root.Add(newValue) — Matthew E Cornish
– Matthew E Cornish, Commented Oct 29, 2018 at 12:25
newFormTemplateXML.Descendants("question").Where(q => (int) q.Attribute("id") == 1).Single().Add(new XElement("boo")) works for me. — Jeroen Mostert
– Jeroen Mostert, Commented Oct 29, 2018 at 12:26
@JeroenMostert ooo that worked, thank you - do you want to post that up as an answer? — Matthew E Cornish
– Matthew E Cornish, Commented Oct 29, 2018 at 12:32

Jeroen Mostert · Accepted Answer · 2018-10-29 12:38:21Z

3

Using the "native" methods:

newFormTemplateXML
    .Descendants("question")
    .Single(q => (int) q.Attribute("id") == 1)
    .Add(newValue);

Or, for XPath lovers:

newFormTemplateXML.XPathSelectElement("//question[@id=1]").Add(newValue);

Note that this doesn't verify there is really only one question with id 1, it will modify only the first such question. The Single() call doesn't have this problem/advantage.

answered Oct 29, 2018 at 12:38

Jeroen Mostert

29k2 gold badges60 silver badges92 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jamie · Accepted Answer · 2018-10-29 12:37:06Z

0

Append doesn't do what you think it does. Append adds a new item to the end of a sequence and you are not wanting to add to the descendants.

XDocument newFormTemplateXML = XDocument.Load("newFormTemplate.xml");
XElement newvalue = new XElement("value", 123);
var question = newFormTemplateXML.Descendants()
    .Where(d => d.Name.ToString().Equals("question") &&   
        d.Attribute("id").Equals(1)).SingleOrDefault();
question.add(newValue)
newFormTemplateXML.Save("test.xml");

answered Oct 29, 2018 at 12:37

Jamie

3,3671 gold badge22 silver badges28 bronze badges

Collectives™ on Stack Overflow

C# Add element to existing XML

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related