how to change child node's text value in an xml file using c#

Question

I've tried searching for the solution before asking it myself but I haven't found what I was looking for.

<bookstore>


<book category="cooking">
    <title lang="en">Everyday Italian</title>
    <author>Giada De Laurentiis</author>
    <year>2005</year>
    <price>30.00</price>
  </book>
  <book category="children">
    <title lang="en">Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
  </book>

In the example above, say I want to change the text vaule "Harry Potter" to something else, what is the simplest way to do it

Answer 1

XDocument and LINQ to XML gives you a very expressive way of doing this.

// Parse our xml into an XDocument, which is a tree of nodes and collections of XElements, which represent xml elements
var xdoc = XDocument.Parse(
@"<bookstore>
  <book category=""cooking"">
     <title lang=""en"">Everyday Italian</title>
     <author>Giada De Laurentiis</author>
     <year>2005</year>
     <price>30.00</price>
  </book>
  <book category=""children"">
      <title lang=""en"">Harry Potter</title>
      <author>J K. Rowling</author>
      <year>2005</year>
      <price>29.99</price>
  </book>
  </bookstore>");

var book = xdoc
           // Start with the root node (bookstore)
           .Root
           // Take the child elements (books)
           .Elements()
           // Take 1, and only 1 book element such that it contains a title element with the value "Harry Potter"
           .Single(x => x.Element("title").Value == "Harry Potter");

// Set this books title element to the new title
book.Element("title").SetValue("NEW TITLE");
// Any changes we make alters the underlying XDocument, so we can print the final result.
Console.Write(xdoc.ToString());

For more info, read chapter 10 of C# 6.0 in a Nutshell.

Answer 2

This is another way of achieving what you are after. A lot more code than what Stuart has provided. But I prefer this method as this is type safe and will stop you enter text in a number field.

#region Usings

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

#endregion

public class Program
{
    /// <summary>
    /// This method reads an xml file.
    /// Finds the element to change.
    /// Changes the Title.
    /// And Finally saves the changes back to the xml file.
    /// </summary>
    public void Main()
    {
        // The file path of the XML document.
        string filePath = "document.xml";

        // Initializing the book store variable.
        BookStore bookStore = null;

        // Initializing the reading and writing of the XML file.
        using (StreamReader fileReadStream = new StreamReader(filePath))
        using (StreamWriter fileWriteStream = new StreamWriter(filePath))
        {
            // Initializing the serializer.
            XmlSerializer serializer = new XmlSerializer(typeof(BookStore));

            // De-serializing the XML file to objects.
            bookStore = (BookStore)serializer.Deserialize(fileReadStream);

            // Finding the required element.
            Book book = bookStore.Book.Single(b => b.Category.Equals("children") &&
                                                   b.Title.Lang.Equals("en") &&
                                                   b.Title.Value.Equals("Harry Potter"));

            // Setting the new title of the book.
            book.Title.Value = "New Title";


            // Saving the changes back to the XML file.
            serializer.Serialize(fileWriteStream, bookStore);
        }
    }
}

#region BookStore Classes

/// <remarks/>
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
[System.Xml.Serialization.XmlRootAttribute(Namespace = "", IsNullable = false)]
public partial class BookStore
{
    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute("book")]
    public IEnumerable<Book> Book { get; set; }

}

/// <remarks/>
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
public partial class Book
{
    /// <remarks/>
    public BookStoreBookTitle Title { get; set; }

    /// <remarks/>
    public string Author { get; set; }

    /// <remarks/>
    public ushort Year { get; set; }

    /// <remarks/>
    public decimal Price { get; set; }

    /// <remarks/>
    [System.Xml.Serialization.XmlAttributeAttribute()]
    public string Category { get; set; }
}

/// <remarks/>
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
public partial class BookStoreBookTitle
{
    /// <remarks/>
    [System.Xml.Serialization.XmlAttributeAttribute()]
    public string Lang { get; set; }

    /// <remarks/>
    [System.Xml.Serialization.XmlTextAttribute()]
    public string Value { get; set; }
}

#endregion

Hope this helps.