C# XmlReader, Parse XML File
Use the XmlReader class for fast XML file reading. XmlReader scans files for important data.XmlReader opens and parses XML files. It handles attribute values, text nodes and multiple tag names. It provides a lower-level abstraction over the XML file structure. This is more complex than other solutions but benefits performance.
XmlWriter Conceptually, the XmlReader provides a forward-only parsing object for the underlying XML files. In other words, you must manage the position in the file logically in your code as the parser can only go forward.
Info: XmlReader reduces the memory space required for the parser. It is efficient.
Example. You can use certain methods, such as IsStartElement and the Name property, to detect the location in the file and then execute conditional logic based on this location. This increases complexity.
PropertyCreate: We instantiate an XmlReader instance by assigning an XmlReader reference to the result of the XmlReader.Create static method.
While: We see a while-loop construct that evaluates the result of the Read instance method in its expression body.
WhileIsStartElement: This returns true if the element is not an end tag. It returns true for "<article>" but false for "</article>".
Name: The attribute "name" is accessed with the "name" argument in an indexer. This is null when not found.
Indexer C# program that uses XmlReader type
using System;
using System.Xml;
class Program
{
static void Main()
{
// Create an XML reader for this file.
using (
XmlReader reader = XmlReader.Create(
"perls.xml"))
{
while (reader.Read())
{
// Only detect start elements.
if (reader.IsStartElement())
{
// Get element name and switch on it.
switch (reader.Name)
{
case "perls":
// Detect this element.
Console.WriteLine(
"Start <perls> element.");
break;
case "article":
// Detect this article element.
Console.WriteLine(
"Start <article> element.");
// Search for the attribute name on this current node.
string attribute = reader["name"];
if (attribute != null)
{
Console.WriteLine(
" Has attribute name: " + attribute);
}
// Next read will contain text.
if (reader.Read())
{
Console.WriteLine(
" Text node: " + reader.Value.Trim());
}
break;
}
}
}
}
}
}
Input text: perls.xml
<?xml version="1.0" encoding="utf-8" ?>
<perls>
<article name="backgroundworker">
Example text.
</article>
<article name="threadpool">
More text.
</article>
<article></article>
<article>Final text.</article>
</perls>
Output
Start <perls> element.
Start <article> element.
Has attribute name: backgroundworker
Text node: Example text.
Start <article> element.
Has attribute name: threadpool
Text node: More text.
Start <article> element.
Text node:
Start <article> element.
Text node: Final text.
Benefits. Let's review the benefits of XmlReader as opposed to some solutions such as the XElement type. Unfortunately, the XmlReader will introduce more complexity into the parsing code in your program, due to its nature as a forward-only parser.
And: XmlReader will not parse an entire file into an object model automatically.
Types such as XElement can do this, as with the XElement.Load method. But they can greatly expand memory usage and reduce performance by forcing unnecessary disk IO and allocations.
XElement Summary. We looked at a simple example of the XmlReader type in the C# language. This class can be used to implement higher-level parsing code, while retaining top performance and low memory usage.
Thus: The XmlReader retains more complexity. With it you can manipulate the XML at a level more suited to many programs.
© 2007-2020 Sam Allen. Send bug reports to info@dotnetperls.com.