[c#] How does one parse XML files?

Is there a simple method of parsing XML files in C#? If so, what?

I'm not sure whether "best practice for parsing XML" exists. There are numerous technologies suited for different situations. Which way to use depends on the concrete scenario.

You can go with LINQ to XML, XmlReader, XPathNavigator or even regular expressions. If you elaborate your needs, I can try to give some suggestions.

You can parse the XML using this library System.Xml.Linq. Below is the sample code I used to parse a XML file

public CatSubCatList GenerateCategoryListFromProductFeedXML()
{
    string path = System.Web.HttpContext.Current.Server.MapPath(_xmlFilePath);

    XDocument xDoc = XDocument.Load(path);

    XElement xElement = XElement.Parse(xDoc.ToString());


    List<Category> lstCategory = xElement.Elements("Product").Select(d => new Category
    {
        Code = Convert.ToString(d.Element("CategoryCode").Value),
        CategoryPath = d.Element("CategoryPath").Value,
        Name = GetCateOrSubCategory(d.Element("CategoryPath").Value, 0), // Category
        SubCategoryName = GetCateOrSubCategory(d.Element("CategoryPath").Value, 1) // Sub Category
    }).GroupBy(x => new { x.Code, x.SubCategoryName }).Select(x => x.First()).ToList();

    CatSubCatList catSubCatList = GetFinalCategoryListFromXML(lstCategory);

    return catSubCatList;
}

You can use XmlDocument and for manipulating or retrieve data from attributes you can Linq to XML classes.

I have just recently been required to work on an application which involved the parsing of an XML document and I agree with Jon Galloway that the LINQ to XML based approach is, in my opinion, the best. I did however have to dig a little to find usable examples, so without further ado, here are a few!

Any comments welcome as this code works but may not be perfect and I would like to learn more about parsing XML for this project!

public void ParseXML(string filePath)  
{  
    // create document instance using XML file path
    XDocument doc = XDocument.Load(filePath);

    // get the namespace to that within of the XML (xmlns="...")
    XElement root = doc.Root;
    XNamespace ns = root.GetDefaultNamespace();

    // obtain a list of elements with specific tag
    IEnumerable<XElement> elements = from c in doc.Descendants(ns + "exampleTagName") select c;

    // obtain a single element with specific tag (first instance), useful if only expecting one instance of the tag in the target doc
    XElement element = (from c in doc.Descendants(ns + "exampleTagName" select c).First();

    // obtain an element from within an element, same as from doc
    XElement embeddedElement = (from c in element.Descendants(ns + "exampleEmbeddedTagName" select c).First();

    // obtain an attribute from an element
    XAttribute attribute = element.Attribute("exampleAttributeName");
}

With these functions I was able to parse any element and any attribute from an XML file no problem at all!

Use a good XSD Schema to create a set of classes with xsd.exe and use an XmlSerializer to create a object tree out of your XML and vice versa. If you have few restrictions on your model, you could even try to create a direct mapping between you model classes and the XML with the Xml*Attributes.

There is an introductory article about XML Serialisation on MSDN.

Performance tip: Constructing an XmlSerializer is expensive. Keep a reference to your XmlSerializer instance if you intend to parse/write multiple XML files.

You can use ExtendedXmlSerializer to serialize and deserialize.

Instalation You can install ExtendedXmlSerializer from nuget or run the following command:

Install-Package ExtendedXmlSerializer

Serialization:

ExtendedXmlSerializer serializer = new ExtendedXmlSerializer();
var obj = new Message();
var xml = serializer.Serialize(obj);

Deserialization

var obj2 = serializer.Deserialize<Message>(xml);

Standard XML Serializer in .NET is very limited.

• Does not support serialization of class with circular reference or class with interface property,
• Does not support Dictionaries,
• There is no mechanism for reading the old version of XML,
• If you want create custom serializer, your class must inherit from IXmlSerializable. This means that your class will not be a POCO class,
• Does not support IoC.

ExtendedXmlSerializer can do this and much more.

ExtendedXmlSerializer support .NET 4.5 or higher and .NET Core. You can integrate it with WebApi and AspCore.

Use XmlTextReader, XmlReader, XmlNodeReader and the System.Xml.XPath namespace. And (XPathNavigator, XPathDocument, XPathExpression, XPathnodeIterator).

Usually XPath makes reading XML easier, which is what you might be looking for.

If you're using .NET 2.0, try XmlReader and its subclasses XmlTextReader, and XmlValidatingReader. They provide a fast, lightweight (memory usage, etc.), forward-only way to parse an XML file.

If you need XPath capabilities, try the XPathNavigator. If you need the entire document in memory try XmlDocument.

If you're processing a large amount of data (many megabytes) then you want to be using XmlReader to stream parse the XML.

Anything else (XPathNavigator, XElement, XmlDocument and even XmlSerializer if you keep the full generated object graph) will result in high memory usage and also a very slow load time.

Of course, if you need all the data in memory anyway, then you may not have much choice.

In Addition you can use XPath selector in the following way (easy way to select specific nodes):

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

var found = doc.DocumentElement.SelectNodes("//book[@title='Barry Poter']"); // select all Book elements in whole dom, with attribute title with value 'Barry Poter'

// Retrieve your data here or change XML here:
foreach (XmlNode book in nodeList)
{
  book.InnerText="The story began as it was...";
}

Console.WriteLine("Display XML:");
doc.Save(Console.Out);

the documentation

It's very simple. I know these are standard methods, but you can create your own library to deal with that much better.

Here are some examples:

XmlDocument xmlDoc= new XmlDocument(); // Create an XML document object
xmlDoc.Load("yourXMLFile.xml"); // Load the XML document from the specified file

// Get elements
XmlNodeList girlAddress = xmlDoc.GetElementsByTagName("gAddress");
XmlNodeList girlAge = xmlDoc.GetElementsByTagName("gAge"); 
XmlNodeList girlCellPhoneNumber = xmlDoc.GetElementsByTagName("gPhone");

// Display the results
Console.WriteLine("Address: " + girlAddress[0].InnerText);
Console.WriteLine("Age: " + girlAge[0].InnerText);
Console.WriteLine("Phone Number: " + girlCellPhoneNumber[0].InnerText);

Also, there are some other methods to work with. For example, here. And I think there is no one best method to do this; you always need to choose it by yourself, what is most suitable for you.