Reading data from XML

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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.


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);  
}

Alternatively, you can use XPathNavigator:

XmlDocument doc = new XmlDocument();
doc.LoadXml(xml);
XPathNavigator navigator = doc.CreateNavigator();

string books = GetStringValues("Books: ", navigator, "//Book/Title");
string authors = GetStringValues("Authors: ", navigator, "//Book/Author");

..

/// <summary>
/// Gets the string values.
/// </summary>
/// <param name="description">The description.</param>
/// <param name="navigator">The navigator.</param>
/// <param name="xpath">The xpath.</param>
/// <returns></returns>
private static string GetStringValues(string description,
                                      XPathNavigator navigator, string xpath) {
    StringBuilder sb = new StringBuilder();
    sb.Append(description);
    XPathNodeIterator bookNodesIterator = navigator.Select(xpath);
    while (bookNodesIterator.MoveNext())
       sb.Append(string.Format("{0} ", bookNodesIterator.Current.Value));
    return sb.ToString();
}

Try GetElementsByTagName method of XMLDocument class to read specific data or LoadXml method to read all data to xml document.


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