15/06/2015

Interview Questions for Programmers by MK #3

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Question #3
You found the following code and were asked to refactor it if needed:
var sb = new StringBuilder();
sb.AppendLine("<root>")
sb.AppendLine(String.Format("   <node id="{0}"/>", 1));
sb.AppendLine(String.Format("   <node id="{0}"/>", 2));
sb.AppendLine(String.Format("   <node id="{0}"/>", 3));
//Many, many lines of code
sb.AppendLine("</root>");
What would you do and why?

Answer #3
It is not the best idea to create XML documents using string concatenation because it is error prone. Besides created documents are not validated in any way. In .NET we have a few possibilities to refactor this code.

I recommend to use XmlWriter in this case because we want to create a new document and we do not want to edit an existing one. However, if we also want to modify existing XML documents, the good choice will be XDocument or XmlDocument class.

In the case of small XML documents (when performance is not critical) it might be a good idea to use XDocument or XmlDocument even if we don't want to edit existing documents. Especially XDocument can be simpler in use than XmlWriter.

Comments #3
I remember that when I wanted to create an XML document in C# for the first time I did it by using string concatenation. The code worked ok and I was surprised that it didn't pass a review :)

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