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);

Answer 2

This should do the trick. It is a console app, but the principle is exactly the same. It does assume a file called "web.config" will be in the same folder as the exe:

using System;
using System.Xml;

namespace ConsoleApplication7
{
    class Program
    {
        static void Main(string[] args)
        {
            var document = new XmlDocument();
            document.Load("web.config");

            var element = document.SelectSingleNode("//compilation[@defaultLanguage = 'c#' and @debug = 'true']");

            var comment = document.CreateComment(element.OuterXml);

            element.ParentNode.ReplaceChild(comment, element);

            document.Save("web.config2");

            var document2 = new XmlDocument();
            document2.Load("web.config2");

            var comment2 = document2.SelectSingleNode("//system.web/comment()");
            var newNode = document2.CreateDocumentFragment();
            newNode.InnerXml = comment2.InnerText;
            comment2.ParentNode.ReplaceChild(newNode, comment2);
            document2.Save("web.config3");

            Console.ReadKey();
        }
    }
}

It's saving to different files to show the progression of the xml, obviously, you'd just want to save back to the original file.

edit: You changed the xml since I wrote the answer, but if you change the xpath then it should work exactly the same.

Answer 3

the problem here is that an XmlDocument is a data structure for a load of XML, it will not read in the comments when it parses the file. you are trying to edit the file itself.