Linq to XML - remove a node and add a new node at same place

Question

I have an XDocument and have to remove a node and add the very same node back again after some manipulation(my xelement node are complex and have inner nodes as well). Has anyone got a good way to do this as my new manipulated node is being added at the very end of the xmldocument. Any code snippets would be greatly appreciated.

Answer 1

If I understand you right, this should help you do it.

SolarSystem.xml:

<?xml version="1.0" encoding="UTF-8"?>
<SolarSystem>
  <Planets>
    <Planet Id="1">
      <Name>Mercury</Name>
    </Planet>
    <Planet Id="2">
      <Name>Venus</Name>
    </Planet>
    <Planet Id="3">
      <Name>Earth</Name>
    </Planet>
  </Planets>
</SolarSystem>

The code finds the <Planet> Mercury, adds an extra element to it, removes it, and reinserts it at the end of the <Planets> collection.

XDocument SolarSystem = XDocument.Load(Server.MapPath("SolarSystem.xml"));
IEnumerable<XElement> Planets = SolarSystem.Element("SolarSystem").Element("Planets").Elements("Planet");

// identify and change Mercury
XElement Mercury = Planets.Where(p => p.Attribute("Id").Value == "1").FirstOrDefault();
Mercury.Add(new XElement("YearLengthInDays", "88"));

// remove Mercury from current position, and add back in at the end
Mercury.Remove();
Planets.Last().AddAfterSelf(Mercury);

// save it as new file
SolarSystem.Save(Server.MapPath("NewSolarSystem.xml"));

which gives:

<?xml version="1.0" encoding="UTF-8"?>
   <SolarSystem>
     <Planets>
       <Planet Id="2">
         <Name>Venus</Name>
       </Planet>
       <Planet Id="3">
         <Name>Earth</Name>
       </Planet>
       <Planet Id="1">
         <Name>Mercury</Name>
         <YearLengthInDays>88</YearLengthInDays>
       </Planet>
     </Planets>
   </SolarSystem>

Answer 2

If you're just editing the node, then why remove it at all? Just get a reference to it in the tree and edit it in-place.

If that's not an option for some reason, then one way to go about it is this: once you've found the XElement (or, in general, XNode) you need to replace in the tree, create a new XElement to serve as a replacement, and then use XNode.ReplaceWith method on the old element, passing new one as the argument.

Answer 3

This just builds on @Ralph Lavelle's example above. I created a complete console app so I could play with the code & understand it better. Figured I'd share it. It uses the exact same sample XML from above, but I had to remove the references to Server.MapPath() as I couldn't figure out how to make them work. Here you go:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

class LinqDemo
{
static void Main( )
    {
        XDocument SolarSystem = XDocument.Load("SolarSystem.xml");
        IEnumerable<XElement> Planets = SolarSystem.Element("SolarSystem").Element("Planets").Elements("Planet");

        // identify and change Mercury
        XElement Mercury = Planets.Where(p => p.Attribute("Id").Value == "1").FirstOrDefault();
        Mercury.Add(new XElement("YearLengthInDays", "88"));

        // remove Mercury from current position, and add back in at the end
        Mercury.Remove();
        Planets.Last().AddAfterSelf(Mercury);

        // save it as new file
        SolarSystem.Save("NewSolarSystem.xml");
    }
}

Maybe this'll help another LINQ noob like me.