[c#] How do I read and parse an XML file in C#?

How do I read and parse an XML file in C#?

LINQ to XML Example:

// Loading from a file, you can also load from a stream
var xml = XDocument.Load(@"C:\contacts.xml");


// Query the data and write out a subset of contacts
var query = from c in xml.Root.Descendants("contact")
            where (int)c.Attribute("id") < 4
            select c.Element("firstName").Value + " " +
                   c.Element("lastName").Value;


foreach (string name in query)
{
    Console.WriteLine("Contact's Full Name: {0}", name);
}

Reference: LINQ to XML at MSDN

Linq to XML.

Also, VB.NET has much better xml parsing support via the compiler than C#. If you have the option and the desire, check it out.

Check out XmlTextReader class for instance.

There are different ways, depending on where you want to get. XmlDocument is lighter than XDocument, but if you wish to verify minimalistically that a string contains XML, then regular expression is possibly the fastest and lightest choice you can make. For example, I have implemented Smoke Tests with SpecFlow for my API and I wish to test if one of the results in any valid XML - then I would use a regular expression. But if I need to extract values from this XML, then I would parse it with XDocument to do it faster and with less code. Or I would use XmlDocument if I have to work with a big XML (and sometimes I work with XML's that are around 1M lines, even more); then I could even read it line by line. Why? Try opening more than 800MB in private bytes in Visual Studio; even on production you should not have objects bigger than 2GB. You can with a twerk, but you should not. If you would have to parse a document, which contains A LOT of lines, then this documents would probably be CSV.

I have written this comment, because I see a lof of examples with XDocument. XDocument is not good for big documents, or when you only want to verify if there the content is XML valid. If you wish to check if the XML itself makes sense, then you need Schema.

I also downvoted the suggested answer, because I believe it needs the above information inside itself. Imagine I need to verify if 200M of XML, 10 times an hour, is valid XML. XDocument will waste a lof of resources.

prasanna venkatesh also states you could try filling the string to a dataset, it will indicate valid XML as well.

Here's an application I wrote for reading xml sitemaps:

using System;
using System.Collections.Generic;
using System.Windows.Forms; 
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Data;
using System.Xml;

namespace SiteMapReader
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Please Enter the Location of the file");

            // get the location we want to get the sitemaps from 
            string dirLoc = Console.ReadLine();

            // get all the sitemaps 
            string[] sitemaps = Directory.GetFiles(dirLoc);
            StreamWriter sw = new StreamWriter(Application.StartupPath + @"\locs.txt", true);

            // loop through each file 
            foreach (string sitemap in sitemaps)
            {
                try
                {
                    // new xdoc instance 
                    XmlDocument xDoc = new XmlDocument();

                    //load up the xml from the location 
                    xDoc.Load(sitemap);

                    // cycle through each child noed 
                    foreach (XmlNode node in xDoc.DocumentElement.ChildNodes)
                    {
                        // first node is the url ... have to go to nexted loc node 
                        foreach (XmlNode locNode in node)
                        {
                            // thereare a couple child nodes here so only take data from node named loc 
                            if (locNode.Name == "loc")
                            {
                                // get the content of the loc node 
                                string loc = locNode.InnerText;

                                // write it to the console so you can see its working 
                                Console.WriteLine(loc + Environment.NewLine);

                                // write it to the file 
                                sw.Write(loc + Environment.NewLine);
                            }
                        }
                    }
                }
                catch { }
            }
            Console.WriteLine("All Done :-)"); 
            Console.ReadLine(); 
        }

        static void readSitemap()
        {
        }
    }
}

Code on Paste Bin http://pastebin.com/yK7cSNeY

There are lots of way, some:

• XmlSerializer. use a class with the target schema you want to read - use XmlSerializer to get the data in an Xml loaded into an instance of the class.
• Linq 2 xml
• XmlTextReader.
• XmlDocument
• XPathDocument (read-only access)

  public void ReadXmlFile()
    {
        string path = HttpContext.Current.Server.MapPath("~/App_Data"); // Finds the location of App_Data on server.
        XmlTextReader reader = new XmlTextReader(System.IO.Path.Combine(path, "XMLFile7.xml")); //Combines the location of App_Data and the file name
        while (reader.Read())
        {
            switch (reader.NodeType)
            {
                case XmlNodeType.Element:
                    break;
                case XmlNodeType.Text:
                    columnNames.Add(reader.Value);
                    break;
                case XmlNodeType.EndElement:
                    break;
            }
        }
    }

You can avoid the first statement and just specify the path name in constructor of XmlTextReader.

XmlDocument to read an XML from string or from file.

XmlDocument doc = new XmlDocument();
doc.Load("c:\\temp.xml");

or

doc.LoadXml("<xml>something</xml>");

then find a node below it ie like this

XmlNode node = doc.DocumentElement.SelectSingleNode("/book/title");

or

foreach(XmlNode node in doc.DocumentElement.ChildNodes){
   string text = node.InnerText; //or loop through its children as well
}

then read the text inside that node like this

string text = node.InnerText;

or read an attribute

string attr = node.Attributes["theattributename"]?.InnerText

Always check for null on Attributes["something"] since it will be null if the attribute does not exist.

You could use a DataSet to read XML strings.

var xmlString = File.ReadAllText(FILE_PATH);
var stringReader = new StringReader(xmlString);
var dsSet = new DataSet();
dsSet.ReadXml(stringReader);

Posting this for the sake of information.

If you want to retrive a particular value from an XML file

 XmlDocument _LocalInfo_Xml = new XmlDocument();
            _LocalInfo_Xml.Load(fileName);
            XmlElement _XmlElement;
            _XmlElement = _LocalInfo_Xml.GetElementsByTagName("UserId")[0] as XmlElement;
            string Value = _XmlElement.InnerText;

You can either:

• Use XmlSerializer class
• Use XmlDocument class

Examples are on the msdn pages provided