Create tag in XML with C#

Question

I have a very frustrating issue which I'm hoping will actually be something extremely simple. Apologies in advance if my terminology in XML files is wrong.

Basically I have a fairly simple XML file, here is an extract of one node:

<Attr num="108" name="Title" desc="The title of this file." type="s" ord="1" value="Test Title">

I can read and write the value key of the node fairly easily, but only if the value key exists.

I can use this code to write values back to the file:

XmlNode node = xmlDoc.SelectSingleNode("//ma:Attr[@name='Title']/@value", ns);
node.Value = partname.Text;
xmlDoc.Save(sympath);

However, if the XML file has the node of the correct name, but does not have a value key then it fails. For example, in some files the XML looks like this:

<Attr num="108" name="Title" desc="The title of this file." type="s" ord="1">

So I'm going round and round in circles just trying to add value="something" to that node if it doesn't already exist. Is there a way to do this? I can add child elements, but I just want to add the value in that string!

I have tried searching for an answer, but all the other similar issues seem to be about adding or modifying child elements.

Thank you,
Andrew

If I understand you right you want to create the attribute value if it doesn't exist. If that is the case take a look at this answer — Prajnan Bhuyan
– Prajnan Bhuyan, Commented Feb 8, 2018 at 8:55

har07 · Accepted Answer · 2018-02-08 11:02:07Z

2

Actually, XmlElement.SetAttribute() alone did the job :

var node = (XmlElement)xmlDoc.SelectSingleNode("//ma:Attr[@name='Title']", ns);
node.SetAttribute("value", partname.Text);

Select parent element instead of the attribute, check if value attribute exists in that element and take action accordingly i.e add attribute or just update the value :

var node = (XmlElement)xmlDoc.SelectSingleNode("//ma:Attr[@name='Title']", ns);
var attr = node.Attributes["value"];
if(attr != null)
{
    attr.Value = partname.Text;
}   
else 
{
    node.SetAttribute("value", partname.Text);
}

edited Feb 8, 2018 at 11:02

answered Feb 8, 2018 at 9:06

har07

89.5k12 gold badges87 silver badges143 bronze badges

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

6 Comments

Andrew Taylor Over a year ago

looks like some great code, but i can't get it to work. Firstly I get an error because the var attr is null if value doesn't exist. Also, I don't see node.setattribute. I have tried using XmlAttribute...

har07 Over a year ago

@AndrewTaylor sorry, node should be of type XmlElement. If there is a possibility of SelectSingleNode returning null then you'll need to check the return value first before casting to XmlElement...

Andrew Taylor Over a year ago

ok that is almost working now. I'm having trouble if value doesn't exist still. I've tried using if node.hasattribute("value"), but it's still returning null and throwing up an error. Any more pointers?! Sorry to be a pain

har07 Over a year ago

The code in this answer does the check already, so I'm not sure how you adapted this code. Hopefully live demo can help you to understand better: dotnetfiddle.net/Dht4FC

har07 Over a year ago

Ah, actually you can just call SetAttribute() without checking if the attribute exists first... answer updated.. and the demo as well

|

Collectives™ on Stack Overflow

Create tag in XML with C#

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related