How to comment a line of a XML file in C# with System.XML

Question

I need to comment and uncomment the 4th line of this XML file using System.XML properties:

<?xml version="1.0" encoding="utf-8"?>
    <configuration>    
        <system.web>
            <customErrors mode="On" defaultRedirect="som_url_here" />
        </system.web>
    </configuration>

Desired output:

<!-- <customErrors mode="On" defaultRedirect="som_url_here" /> -->

It's possible to achieve this without using a file reader?

The node:

XmlNode xmlNodoCE = docWebConfig.DocumentElement.SelectSingleNode("system.web/customErrors");

Answer 1

You need to

• load the file into an XmlDocument,
• retrieve the node you want to comment,
• create a comment node containing the XML content of your original node,
• add this comment to the original's parent node just before the original node
• remove it from its parent,

• write the XmlDocument to a file (the same one).

  String xmlFileName = "Sample.xml";
  
  // Find the proper path to the XML file
  String xmlFilePath = this.Server.MapPath(xmlFileName);
  
  // Create an XmlDocument
  System.Xml.XmlDocument xmlDocument = new System.Xml.XmlDocument();
  
  // Load the XML file in to the document
  xmlDocument.Load(xmlFilePath);
  
  // Get the target node using XPath
  System.Xml.XmlNode elementToComment = xmlDocument.SelectSingleNode("/configuration/system.web/customErrors");
  
  // Get the XML content of the target node
  String commentContents = elementToComment.OuterXml;
  
  // Create a new comment node
  // Its contents are the XML content of target node
  System.Xml.XmlComment commentNode = xmlDocument.CreateComment(commentContents);
  
  // Get a reference to the parent of the target node
  System.Xml.XmlNode parentNode = elementToComment.ParentNode;
  
  // Replace the target node with the comment
  parentNode.ReplaceChild(commentNode, elementToComment);
  
  xmlDocument.Save(xmlFilePath);