Quickly Changing Values of XML Elements Using LINQ

I've had many questions lately on how you can query for a specific node in an XML document (or fragment) and change it's value using LINQ. (This must mean that people are really starting to use this stuff so I'm pretty excited.) This is really easy to do because you can modify the values of the selected XElements from your queries and that will change the source XML.

Here's an example:

Imports <xmlns="urn:mycompany:examples:plants">

Module Module1

    Sub Main()
        Dim plants = <?xml version="1.0" encoding="ISO-8859-1"?>
                     <CATALOG xmlns="urn:mycompany:examples:plants">
                         <PLANT>
                             <COMMON>Bloodroot</COMMON>
                             <BOTANICAL>Sanguinaria canadensis</BOTANICAL>
                             <ZONE>4</ZONE>
                             <LIGHT>Mostly Shady</LIGHT>
                             <PRICE>$2.44</PRICE>
                             <AVAILABILITY>031599</AVAILABILITY>
                         </PLANT>
                         <PLANT>
                             <COMMON>Columbine</COMMON>
                             <BOTANICAL>Aquilegia canadensis</BOTANICAL>
                             <ZONE>3</ZONE>
                             <LIGHT>Mostly Shady</LIGHT>
                             <PRICE>$9.37</PRICE>
                             <AVAILABILITY>030699</AVAILABILITY>
                         </PLANT>
                         <PLANT>
                             <COMMON>Marsh Marigold</COMMON>
                             <BOTANICAL>Caltha palustris</BOTANICAL>
                             <ZONE>4</ZONE>
                             <LIGHT>Mostly Sunny</LIGHT>
                             <PRICE>$6.81</PRICE>
                             <AVAILABILITY>051799</AVAILABILITY>
                         </PLANT>
                     </CATALOG>

        Dim q = From plant In plants...<PLANT> _
                Where plant.<COMMON>.Value = "Columbine" _
                Select plant

        For Each item In q
            q.<PRICE>.Value = "$49.99"
            q.<LIGHT>.Value = "Full Sun"
        Next

        plants.Save("plants.xml")
     
    End Sub

End Module

Couple things to note above, remember to import any namespaces being used in the XML otherwise your query will yield no results. And remember you can get XML IntelliSense if you import a schema (this is really easy, watch this). Of course, you can load the XML from a file (or URI) instead of using a literal and and get the same results.

Dim plants = XDocument.Load("plants.xml")

Dim q = From plant In plants...<PLANT> _
        Where plant.<COMMON>.Value = "Columbine" _
        Select plant

For Each item In q
    q.<PRICE>.Value = "$49.99"
    q.<LIGHT>.Value = "Full Sun"
Next

plants.Save("plants.xml")

In this example we're overwriting the source document, plants.xml, with our new values. Both examples produce this resulting XML:

<?xml version="1.0" encoding="iso-8859-1"?>
<CATALOG xmlns="urn:mycompany:examples:plants">
  <PLANT>
    <COMMON>Bloodroot</COMMON>
    <BOTANICAL>Sanguinaria canadensis</BOTANICAL>
    <ZONE>4</ZONE>
    <LIGHT>Mostly Shady</LIGHT>
    <PRICE>$2.44</PRICE>
    <AVAILABILITY>031599</AVAILABILITY>
  </PLANT>
  <PLANT>
    <COMMON>Columbine</COMMON>
    <BOTANICAL>Aquilegia canadensis</BOTANICAL>
    <ZONE>3</ZONE>
    <LIGHT>Full Sun</LIGHT>
    <PRICE>$49.99</PRICE>
    <AVAILABILITY>030699</AVAILABILITY>
  </PLANT>
  <PLANT>
    <COMMON>Marsh Marigold</COMMON>
    <BOTANICAL>Caltha palustris</BOTANICAL>
    <ZONE>4</ZONE>
    <LIGHT>Mostly Sunny</LIGHT>
    <PRICE>$6.81</PRICE>
    <AVAILABILITY>051799</AVAILABILITY>
  </PLANT>
</CATALOG>