The following example adds an attribute to an element. : Xml Atrributes « XML « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. XML
3. Xml Atrributes

using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {

    XmlDocument doc = new XmlDocument();
    doc.LoadXml("<book xmlns:bk='urn:samples' bk:ISBN='11111111111'><title>A</title></book>");
    XmlElement root = doc.DocumentElement;

    XmlAttribute attr = root.SetAttributeNode("genre", "urn:samples");
    attr.Value="novel";

    Console.WriteLine(doc.InnerXml);

  }
}