Reading data from XML [duplicate]

Question

I'm planning to use XML for database purpose. Only thing I was able to do is read whole XML file. I want to be able to read only some data and I don't know how to do that.

Here is a simple XML

<Books>
 <Book>
  <Title>Animals</Title>
  <Author>J. Anderson</Author>
 </Book>
 <Book>
  <Title>Car</Title>
  <Author>L. Sawer</Author>
 </Book>
</Books> 

I'm interested in app where output is gonna be

Books:
Animals
Cars

Authors:
J. Anderson
L. Sawer

I'm just want to learn how read specific data from XML not whole file.

[SOLVED] I have used Linq to XML

Answer 1

I don't think you can "legally" load only part of an XML file, since then it would be malformed (there would be a missing closing element somewhere).

Using LINQ-to-XML, you can do var doc = XDocument.Load("yourfilepath"). From there its just a matter of querying the data you want, say like this:

var authors = doc.Root.Elements().Select( x => x.Element("Author") );

HTH.

EDIT:

Okay, just to make this a better sample, try this (with @JWL_'s suggested improvement):

using System;
using System.Xml.Linq;

namespace ConsoleApplication1 {
    class Program {
        static void Main( string[] args )  {
            XDocument doc = XDocument.Load( "XMLFile1.xml" );
            var authors = doc.Descendants( "Author" );
            foreach ( var author in authors ) {
                Console.WriteLine( author.Value );
            }
            Console.ReadLine();
        }
    }
}

You will need to adjust the path in XDocument.Load() to point to your XML file, but the rest should work. Ask questions about which parts you don't understand.

Answer 2

as per @Jon Skeet 's comment, you should use a XmlReader only if your file is very big. Here's how to use it. Assuming you have a Book class

public class Book {
    public string Title {get; set;}
    public string Author {get; set;}
}

you can read the XML file line by line with a small memory footprint, like this:

public static class XmlHelper {
    public static IEnumerable<Book> StreamBooks(string uri) {
        using (XmlReader reader = XmlReader.Create(uri)) {
            string title = null;
            string author = null;

            reader.MoveToContent();
            while (reader.Read()) {
                if (reader.NodeType == XmlNodeType.Element
                    && reader.Name == "Book") {
                    while (reader.Read()) {
                        if (reader.NodeType == XmlNodeType.Element &&
                            reader.Name == "Title") {
                            title = reader.ReadString();
                            break;
                        }
                    }
                    while (reader.Read()) {
                        if (reader.NodeType == XmlNodeType.Element &&
                            reader.Name == "Author") {
                            author =reader.ReadString();
                            break;
                        }
                    }
                    yield return new Book() {Title = title, Author = author};
                }
            }       
        }
    }

Example of usage:

string uri = @"c:\test.xml"; // your big XML file

foreach (var book in XmlHelper.StreamBooks(uri)) {
    Console.WriteLine("Title, Author: {0}, {1}", book.Title, book.Author);  
}