How can I delete specific nodes from an XElement?

Question

I have created a XElement with node which has XML as below.

I want to remove all the "Rule" nodes if they contain "conditions" node.

I create a for loop as below, but it does not delete my nodes:

foreach (XElement xx in xRelation.Elements())
{
  if (xx.Element("Conditions") != null)
  {
    xx.Remove();
  }
}

Sample:

<Rules effectNode="2" attribute="ability" iteration="1">
    <Rule cause="Cause1" effect="I">
      <Conditions>
        <Condition node="1" type="Internal" />
      </Conditions>
    </Rule>
    <Rule cause="cause2" effect="I">
      <Conditions>
        <Condition node="1" type="External" />
      </Conditions>
    </Rule>
</Rules>

How can I remove all the "Rule" nodes if they contain "conditions" node?

Flews

you can't iterate rule elements with foreach while deleting the items. rather you can collection them in a list and the iterate using for loop and delete them. – Gragg

Answer 1

You can try this approach:

var nodes = xRelation.Elements().Where(x => x.Element("Conditions") != null).ToList();

foreach(var node in nodes)
    node.Remove();

Basic idea: you can't delete elements of collection you're currently iterating.
So first you have to create list of nodes to delete and then delete these nodes.

Afraid

The importance of the call to 'ToList()' here to materialise the collection of elements shouldn't be underestimate. Scratched my head for a good few minutes before I landed here and noticed the .ToList() call before the foreach utilisation! (Thank you) – Culprit

Answer 2

You can use LINQ:

xRelation.Elements()
     .Where(el => el.Elements("Conditions") == null)
     .Remove();

Or create a copy of the nodes to delete, and delete them after (in case the first method doesn't work):

List nodesToDelete = xRelation
    .Elements()
    .Where(el => el.Elements("Conditions") == null)
    .ToList();

foreach (XElement el in nodesToDeletes)
{
    // Removes from its parent, but not nodesToDelete
    // itself, so we can use foreach here
    el.Remove();
}

Mousebird

I don't think your solution at the top can work. el.Elements("Conditions") == null) will always evaluate to not null. – Mcneill

@CiaranGallagher well, the answer is 7 years old, but it was upvoted 12 times, so I assume it's been a working solution to OP's issues at the time :) – Mousebird

Answer 3

  passiveLead.DataXml.Descendants("Conditions").Remove();

This will remove all descendant elements that match the name 'Conditions' for the XML document.

Stoss

Can you please add some additional explanation or references for the OP and future readers? – Invidious

Answer 4

I've made a small example for you:

XDocument document = XDocument.Parse(GetXml());
var rulesNode = document.Element("Rules");
if (rulesNode != null)
{
    rulesNode.Elements("Rule").Where(r => r.Element("Conditions") != null).Remove();
}

Hibbert

Answer 5

var el = xRelation.XPathSelectElement("/Rules/Rule/Conditions");
while (el != null)
{
      el.Remove();
      el = xRelation.XPathSelectElement("/Rules/Rule/Conditions");
}

Sparoid

Answer 6

Just an idea:

Reverse the LINQ "condition" and you will get a List without "Rule" nodes.

Isagogics

Hi! Small answers must go in comments section. Please wait till you have enough reputation to comment. See stackoverflow.com/help/how-to-answer – Ehling