Manipulate XML files in c#

Question

I just finished my working code, but still want to improve it.

I want to transform this input:

<item>asdf</item>
<item>asdf</item>
<item>asdf</item>

to this output:

<string name="x1">asdf</string>
<string name="x2">asdf</string>
<string name="x3">asdf</string>

My current code:

 static void Main(string[] args)
 {
 String content;
 using (StreamReader reader = new StreamReader("arrays2.xml"))
 {
 content = reader.ReadToEnd();
 }
 int counter = 0;
 int startIndex = 0;
 while ((startIndex = content.IndexOf("<item>", startIndex)) != -1)
 {
 counter++; 
 content = content.Substring(0, startIndex) + "<string name=\"rule" + counter + "\">" + content.Substring(startIndex + 6);
 }
 content = content.Replace("</item>", "</string>");
 using (StreamWriter writer = new StreamWriter("arrays2_formatted.xml"))
 {
 writer.Write(content);
 }
 Console.WriteLine(content);
 }

I think the bottleneck is in the content assignment within the loop, as a lot of String instance are created and thrown away.

However, is there a completely different way to do this efficiently?

• svick: So, you're saying your code is too slow? Have you profiled it? How big is the file you're converting? Are you sure the code is the bottleneck and not the disk?
• Michael: @svick No, I don't claim anything. I just want to improve it, as I am not a c# developer, normally. :)

Answer 1

Don't parse it through string manipulation, use the XML libraries in the framework. I'd recommend LINQ to XML. Parse it and make your changes.

var xmlStr = @"<root>
<item>asdf</item>
<item>asdf</item>
<item>asdf</item>
</root>";
var doc = XDocument.Parse(xmlStr); // parse from string
//var doc = XDocument.Load("arrays2.xml"); // or load from file
var items = doc.Descendants("item"); // find all item elements
var index = 1;
foreach (var item in items.ToList()) // ToList() required since we're modifying the document
{
 var name = "x" + index++;
 var nameAttr = new XAttribute("name", name); // create the name attribute
 var value = (string)item; // read the value as a string
 var newNode = new XElement("string", nameAttr, value); // create the new element
 item.ReplaceWith(newNode); // replace the current one
}
//doc.Save("arrays2_formatted.xml"); // save the changes to the file

• Jeff Mercado: Note, your "XML" is not valid XML, it needs a root.