how to change xml value file using c#

//Here is the variable with which you assign a new value to the attribute
    string newValue = string.Empty
    XmlDocument xmlDoc = new XmlDocument();

    xmlDoc.Load(xmlFile);

    XmlNode node = xmlDoc.SelectSingleNode("Root/Node/Element");
    node.Attributes[0].Value = newValue;

    xmlDoc.Save(xmlFile);

    //xmlFile is the path of your file to be modified

using System.Xml.Linq;

XDocument xmlFile = XDocument.Load("books.xml");

var query = from c in xmlFile.Elements("catalog").Elements("book")

select c;

foreach (XElement book in query)

{

book.Attribute("attr1").Value = "MyNewValue";

}

xmlFile.Save("books.xml");