C# replace XML node with a new attribute and subnode

Question

I've got this xml file:

<?xml version="1.0"?>
<configuration>
    <configSections>
        <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
        <section name="MyApp.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
        </sectionGroup>
    </configSections>
<startup><supportedRuntime version="v2.0.50727"/></startup>
<applicationSettings>
    <MyApp.Settings>
        ...
        ...
    </XNet.XManager.Properties.Settings>
</applicationSettings>

I need to replace the <startup> node with:

<startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
</startup>

Which is the best way?

Well I'd use LINQ to XML to read the whole document, replace the element you're interested, then write it out again. Have you tried that or anything similar? — Jon Skeet
– Jon Skeet, Commented Feb 15, 2016 at 14:23
What have you tried so far? And you should look into LINQ. It can be scary at first, but its incredibly powerful. — AustinWBryan
– AustinWBryan, Commented Feb 15, 2016 at 14:25
@Sethi: Why? I suspect your reason won't hold water in the long run. The code using LINQ to XML will be simpler than the equivalent using XmlDocument. — Jon Skeet
– Jon Skeet, Commented Feb 15, 2016 at 14:37

w.b · Accepted Answer · 2016-02-16 11:38:48Z

2

If you use LINQ to XML (it's an XML API rather than LINQ):

XDocument doc = XDocument.Load("dat.xml");

XElement startup1 = doc.Root.Element("startup");
startup1.Remove();

doc.Root.Add(new XElement("startup", new XAttribute("useLegacyV2RuntimeActivationPolicy", "true"),
                               new XElement("supportedRuntime", new XAttribute("version", "v4.0"),
                               new XAttribute("sku", ".NETFramework"),
                               new XAttribute("Version", "v4.5.2"))));

doc.Save("dat.xml");

Edit - as Jon Skeet suggested the proper way should be to use XElement.ReplaceWith :

XDocument doc = XDocument.Load("dat.xml");

XElement startup1 = doc.Root.Element("startup");           
startup1.ReplaceWith(new XElement("startup", new XAttribute("useLegacyV2RuntimeActivationPolicy", "true"),
                               new XElement("supportedRuntime", new XAttribute("version", "v4.0"),
                               new XAttribute("sku", ".NETFramework"),
                               new XAttribute("Version", "v4.5.2"))));

doc.Save("dat.xml");

edited Feb 16, 2016 at 11:38

answered Feb 15, 2016 at 15:02

w.b

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3 Comments

Jon Skeet Over a year ago

Possibly nicer - use XElement.ReplaceWith, so it stays in the same location.

Sethi Over a year ago

Oh sorry.. Just doc.Save("dat.xml")... ok.. But: the original version was "<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />" but your code replace the ".NETFramework,Version=.." without the comma: "sku=".NETFramework Version=v4.5.2"

Sethi Over a year ago

Auto answer ;-) : doc.Root.Add(new XElement("startup", new XAttribute("useLegacyV2RuntimeActivationPolicy", "true"), new XElement("supportedRuntime", new XAttribute("version", "v4.0"), new XAttribute("sku", ".NETFramework,Version=v4.5.2"))));

score 0 · Accepted Answer · 2016-02-15 15:02:19Z

0

You can use the below code to do the same, where the element is being find and it is replaced with other.

XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load("path to your file");

string strXml = 
  @"<startup useLegacyV2RuntimeActivationPolicy='true'>
    <supportedRuntime version='v4.0' sku='.NETFramework,Version=v4.5.2' />
</startup>";
XmlDocumentFragment xmlDocFragment = xmlDoc.CreateDocumentFragment();
xmlDocFragment.InnerXml = strXml;
xmlDoc.SelectSingleNode("startup").AppendChild(xmlDocFragment);

Update: Using LINQ. Working Tested Code

var doc = XDocument.Load(@"path to file");
string input = @"<startup useLegacyV2RuntimeActivationPolicy='true'>
<supportedRuntime version='v4.0' sku='.NETFramework,Version=v4.5.2' />
</startup>";
var replacement = XElement.Parse(input);
var nodeToReplace = doc.Descendants().Elements("startup").FirstOrDefault();
nodeToReplace.ReplaceWith(replacement);
doc.Save(@"path to file");
Console.WriteLine(doc);
Console.Read();

edited Feb 15, 2016 at 15:02

answered Feb 15, 2016 at 14:35

user1618825

2 Comments

Jon Skeet Over a year ago

That code won't compile. After fixing it, I'd say it's also significantly less elegant than LINQ to code constructing the elements programmatically.

Jon Skeet Over a year ago

Nope, that's still not going to compile. It's not a valid verbatim string literal.

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