XmlDocument doc = new XmlDocument();
doc.PreserveWhitespace = true;
try { doc.Load("booksData.xml"); }
catch (System.IO.FileNotFoundException)
{
    doc.LoadXml("<?xml version=\"1.0\"?> \n" +
    "<books xmlns=\"http://www.contoso.com/books\"> \n" +
    "  <book genre=\"novel\" ISBN=\"1-861001-57-8\" publicationdate=\"1823-01-28\"> \n" +
    "    <title>Pride And Prejudice</title> \n" +
    "    <price>24.95</price> \n" +
    "  </book> \n" +
    "  <book genre=\"novel\" ISBN=\"1-861002-30-1\" publicationdate=\"1985-01-01\"> \n" +
    "    <title>The Handmaid's Tale</title> \n" +
    "    <price>29.95</price> \n" +
    "  </book> \n" +
    "</books>");             
}

//************************************************************************************
//
//  Associate the schema with XML. Then, load the XML and validate it against
//  the schema.
//
//************************************************************************************
public XmlDocument LoadDocumentWithSchemaValidation(bool generateXML, bool generateSchema)
{
    XmlReader reader;

    XmlReaderSettings settings = new XmlReaderSettings();

    // Helper method to retrieve schema.
    XmlSchema schema = getSchema(generateSchema);

    if (schema == null)
    {
        return null;
    }

    settings.Schemas.Add(schema);

    settings.ValidationEventHandler += settings_ValidationEventHandler;
    settings.ValidationFlags =
        settings.ValidationFlags | XmlSchemaValidationFlags.ReportValidationWarnings;
    settings.ValidationType = ValidationType.Schema;

    try
    {
        reader = XmlReader.Create("booksData.xml", settings);
    }
    catch (System.IO.FileNotFoundException)
    {
        if (generateXML)
        {
            string xml = generateXMLString();
            byte[] byteArray = Encoding.UTF8.GetBytes(xml);
            MemoryStream stream = new MemoryStream(byteArray);
            reader = XmlReader.Create(stream, settings);
        }
        else
        {
            return null;
        }
    }

    XmlDocument doc = new XmlDocument();
    doc.PreserveWhitespace = true;
    doc.Load(reader);
    reader.Close();

    return doc;
}

//************************************************************************************
//
//  Helper method that generates an XML Schema.
//
//************************************************************************************
private string generateXMLSchema()
{
    string xmlSchema =
        "<?xml version=\"1.0\" encoding=\"utf-8\"?> " +
        "<xs:schema attributeFormDefault=\"unqualified\" " +
        "elementFormDefault=\"qualified\" targetNamespace=\"http://www.contoso.com/books\" " +
        "xmlns:xs=\"http://www.w3.org/2001/XMLSchema\"> " +
        "<xs:element name=\"books\"> " +
        "<xs:complexType> " +
        "<xs:sequence> " +
        "<xs:element maxOccurs=\"unbounded\" name=\"book\"> " +
        "<xs:complexType> " +
        "<xs:sequence> " +
        "<xs:element name=\"title\" type=\"xs:string\" /> " +
        "<xs:element name=\"price\" type=\"xs:decimal\" /> " +
        "</xs:sequence> " +
        "<xs:attribute name=\"genre\" type=\"xs:string\" use=\"required\" /> " +
        "<xs:attribute name=\"publicationdate\" type=\"xs:date\" use=\"required\" /> " +
        "<xs:attribute name=\"ISBN\" type=\"xs:string\" use=\"required\" /> " +
        "</xs:complexType> " +
        "</xs:element> " +
        "</xs:sequence> " +
        "</xs:complexType> " +
        "</xs:element> " +
        "</xs:schema> ";
    return xmlSchema;
}

//************************************************************************************
//
//  Helper method that gets a schema
//
//************************************************************************************
private XmlSchema getSchema(bool generateSchema)
{
    XmlSchemaSet xs = new XmlSchemaSet();
    XmlSchema schema;
    try
    {
        schema = xs.Add("http://www.contoso.com/books", "booksData.xsd");
    }
    catch (System.IO.FileNotFoundException)
    {
        if (generateSchema)
        {
            string xmlSchemaString = generateXMLSchema();
            byte[] byteArray = Encoding.UTF8.GetBytes(xmlSchemaString);
            MemoryStream stream = new MemoryStream(byteArray);
            XmlReader reader = XmlReader.Create(stream);
            schema = xs.Add("http://www.contoso.com/books", reader);
        }
        else
        {
            return null;
        }
    }
    return schema;
}

//************************************************************************************
//
//  Helper method to validate the XML against the schema.
//
//************************************************************************************
private void validateXML(bool generateSchema, XmlDocument doc)
{
    if (doc.Schemas.Count == 0)
    {
        // Helper method to retrieve schema.
        XmlSchema schema = getSchema(generateSchema);
        doc.Schemas.Add(schema);
    }

    // Use an event handler to validate the XML node against the schema.
    doc.Validate(settings_ValidationEventHandler);
}

//************************************************************************************
//
//  Event handler that is raised when XML doesn't validate against the schema.
//
//************************************************************************************
void settings_ValidationEventHandler(object sender,
    System.Xml.Schema.ValidationEventArgs e)
{
    if (e.Severity == XmlSeverityType.Warning)
    {
        System.Windows.Forms.MessageBox.Show
            ("The following validation warning occurred: " + e.Message);
    }
    else if (e.Severity == XmlSeverityType.Error)
    {
        System.Windows.Forms.MessageBox.Show
            ("The following critical validation errors occurred: " + e.Message);
        Type objectType = sender.GetType();
    }
}

//引入命名空间
using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {
    //Create the XmlDocument.
    XmlDocument doc = new XmlDocument();
    doc.LoadXml("<?xml version='1.0' ?>" +
                "<book genre='novel' ISBN='1-861001-57-5'>" +
                "<title>Pride And Prejudice</title>" +
                "</book>");

    //Display the document element.
    Console.WriteLine(doc.DocumentElement.OuterXml);
 }
}

//引入命名空间
using System;
using System.IO;
using System.Xml;

public class Sample {

  public static void Main() {

    XmlDocument doc = new XmlDocument();
    doc.LoadXml("<book ISBN='1-861001-57-5'>" +
                "<title>Pride And Prejudice</title>" +
                "<price>19.95</price>" +
                "</book>");

    XmlNode root = doc.FirstChild;

    //Display the contents of the child nodes.
    if (root.HasChildNodes)
    {
      for (int i=0; i<root.ChildNodes.Count; i++)
      {
        Console.WriteLine(root.ChildNodes[i].InnerText);
      }
    }
  }
}

//引入命名空间
using System;
using System.IO;
using System.Xml;

public class Sample {

  public static void Main() {

    XmlDocument doc = new XmlDocument();
    doc.LoadXml("<book ISBN='1-861001-57-5'>" +
                "<title>Pride And Prejudice</title>" +
                "<price>19.95</price>" +
                "</book>");

    XmlNode root = doc.FirstChild;

    Console.WriteLine("Display the price element...");
    Console.WriteLine(root.LastChild.OuterXml);
  }
}

//引入命名空间
using System;
using System.Xml;

public class Sample {

  public static void Main() {

      XmlDocument doc = new XmlDocument();
      doc.Load("books.xml");

      XmlNode currNode = doc.DocumentElement.FirstChild;
      Console.WriteLine("First book...");
      Console.WriteLine(currNode.OuterXml);

      XmlNode nextNode = currNode.NextSibling;
      Console.WriteLine("\r\nSecond book...");
      Console.WriteLine(nextNode.OuterXml); 
  }
}

//引入命名空间
using System;
using System.Xml;

public class Sample {

  public static void Main() {

      XmlDocument doc = new XmlDocument();
      doc.Load("books.xml");

      XmlNode lastNode = doc.DocumentElement.LastChild;
      Console.WriteLine("Last book...");
      Console.WriteLine(lastNode.OuterXml);

      XmlNode prevNode = lastNode.PreviousSibling;
      Console.WriteLine("\r\nPrevious book...");
      Console.WriteLine(prevNode.OuterXml);  
  }
}

public XmlNode GetBook(string uniqueAttribute, XmlDocument doc)
{
    XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
    nsmgr.AddNamespace("bk", "http://www.contoso.com/books");
    string xPathString = "//bk:books/bk:book[@ISBN='" + uniqueAttribute + "']";
    XmlNode xmlNode = doc.DocumentElement.SelectSingleNode(xPathString, nsmgr);
   return xmlNode;
}

public void GetBookInformation(ref string title, ref string ISBN, ref string publicationDate,
    ref string price, ref string genre, XmlNode book)
{
    XmlElement bookElement = (XmlElement)book;

    // Get the attributes of a book.        
    XmlAttribute attr = bookElement.GetAttributeNode("ISBN");
    ISBN = attr.InnerXml;

    attr = bookElement.GetAttributeNode("genre");
    genre = attr.InnerXml;

    attr = bookElement.GetAttributeNode("publicationdate");
    publicationDate = attr.InnerXml;

    // Get the values of child elements of a book.
    title = bookElement["title"].InnerText;
    price = bookElement["price"].InnerText;
}

//引入命名空间
using System;
using System.IO;
using System.Xml;

public class Sample {

  public static void Main() {

    XmlDocument doc = new XmlDocument();
    doc.Load("booksort.xml");

    XmlNodeList nodeList;
    XmlNode root = doc.DocumentElement;

    nodeList=root.SelectNodes("descendant::book[author/last-name='Austen']");
 
    //Change the price on the books.
    foreach (XmlNode book in nodeList)
    {
      book.LastChild.InnerText="15.95";
    }

    Console.WriteLine("Display the modified XML document....");
    doc.Save(Console.Out);
  }
}

//引入命名空间
using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {
    //Create the XmlDocument.
    XmlDocument doc = new XmlDocument();
    doc.Load("books.xml");

    //Display all the book titles.
    XmlNodeList elemList = doc.GetElementsByTagName("title");
    for (int i=0; i < elemList.Count; i++)
    {   
      Console.WriteLine(elemList[i].InnerXml);
    }  
  }
}

public void editBook(string title, string ISBN, string publicationDate,
    string genre, string price, XmlNode book, bool validateNode, bool generateSchema)
{

    XmlElement bookElement = (XmlElement)book;

    // Get the attributes of a book.        
    bookElement.SetAttribute("ISBN", ISBN);
    bookElement.SetAttribute("genre", genre);
    bookElement.SetAttribute("publicationdate", publicationDate);

    // Get the values of child elements of a book.
    bookElement["title"].InnerText = title;
    bookElement["price"].InnerText = price;

    if (validateNode)
    {
        validateXML(generateSchema, bookElement.OwnerDocument);
    }
}

public XmlElement AddNewBook(string genre, string ISBN, string misc, 
    string title, string price, XmlDocument doc)
{
    // Create a new book element.
    XmlElement bookElement = doc.CreateElement("book", "http://www.contoso.com/books");

    // Create attributes for book and append them to the book element.
    XmlAttribute attribute = doc.CreateAttribute("genre");
    attribute.Value = genre;
    bookElement.Attributes.Append(attribute);

    attribute = doc.CreateAttribute("ISBN");
    attribute.Value = ISBN;
    bookElement.Attributes.Append(attribute);

    attribute = doc.CreateAttribute("publicationdate");
    attribute.Value = misc;
    bookElement.Attributes.Append(attribute);

    // Create and append a child element for the title of the book.
    XmlElement titleElement = doc.CreateElement("title");
    titleElement.InnerText = title;
    bookElement.AppendChild(titleElement);

    // Introduce a newline character so that XML is nicely formatted.
    bookElement.InnerXml = 
        bookElement.InnerXml.Replace(titleElement.OuterXml, 
        "\n    " + titleElement.OuterXml + " \n    ");
    
    // Create and append a child element for the price of the book.
    XmlElement priceElement = doc.CreateElement("price");
    priceElement.InnerText= price;
    bookElement.AppendChild(priceElement);

    // Introduce a newline character so that XML is nicely formatted.
    bookElement.InnerXml =
        bookElement.InnerXml.Replace(priceElement.OuterXml, priceElement.OuterXml + "   \n  ");

    return bookElement;
}

public void deleteBook(XmlNode book)
{
    XmlNode prevNode = book.PreviousSibling;
    
    book.OwnerDocument.DocumentElement.RemoveChild(book);

    if (prevNode.NodeType == XmlNodeType.Whitespace || 
        prevNode.NodeType == XmlNodeType.SignificantWhitespace)
    {
        prevNode.OwnerDocument.DocumentElement.RemoveChild(prevNode);
    }
}

//************************************************************************************
//
//  Summary: Move elements up in the XML.
//  
//
//************************************************************************************

public void MoveElementUp(XmlNode book)
{
    XmlNode previousNode = book.PreviousSibling;
    while (previousNode != null && (previousNode.NodeType != XmlNodeType.Element))
    {
        previousNode = previousNode.PreviousSibling;
    }
    if (previousNode != null)
    {
        XmlNode newLineNode = book.NextSibling;
        book.OwnerDocument.DocumentElement.RemoveChild(book);
        if (newLineNode.NodeType == XmlNodeType.Whitespace | 
            newLineNode.NodeType == XmlNodeType.SignificantWhitespace)
        {
            newLineNode.OwnerDocument.DocumentElement.RemoveChild(newLineNode);
        }
        InsertBookElement((XmlElement)book, Constants.positionAbove, 
            previousNode, false, false);
    }
}

//************************************************************************************
//
//  Summary: Move elements down in the XML.
//  
//
//************************************************************************************
public void MoveElementDown(XmlNode book)
{
    // Walk backwards until we find an element - ignore text nodes
    XmlNode NextNode = book.NextSibling;
    while (NextNode != null && (NextNode.NodeType != XmlNodeType.Element))
    {
        NextNode = NextNode.NextSibling;
    }
    if (NextNode != null)
    {
        XmlNode newLineNode = book.PreviousSibling;
        book.OwnerDocument.DocumentElement.RemoveChild(book);
        if (newLineNode.NodeType == XmlNodeType.Whitespace |
            newLineNode.NodeType == XmlNodeType.SignificantWhitespace)
        {
            newLineNode.OwnerDocument.DocumentElement.RemoveChild(newLineNode);
        }

        InsertBookElement((XmlElement)book, Constants.positionBelow, 
            NextNode, false, false);
    }
}

//引入命名空间
using System;
using System.Collections;
using System.Data;
using System.Xml;

public class MainClass {
   public static void Main() {
      XmlDocument doc = new XmlDocument();

      XmlElement root = doc.CreateElement( "books" );
      doc.AppendChild( root );

      XmlElement eltBook = doc.CreateElement( "book" );
      root.AppendChild( eltBook );

      XmlElement eltTitle = doc.CreateElement( "title" );
      eltTitle.AppendChild( doc.CreateTextNode( "myTitle" ) );
      eltBook.AppendChild( eltTitle );

      XmlElement eltAuthor = doc.CreateElement( "author" );
      eltAuthor.AppendChild( doc.CreateTextNode(  "myAuthor" ) );
      eltBook.AppendChild( eltAuthor );

      XmlElement eltPrice = doc.CreateElement( "price" );
      eltPrice.AppendChild( doc.CreateTextNode(  "10.0" ) );
      eltBook.AppendChild( eltPrice );

      Console.WriteLine( doc.OuterXml );
   }
}