title: XML, what is this: null or empty element?
body: <p>Regarding to my other question: <a href="https://stackoverflow.com/questions/7226456/xml-deserialize-null-elements">XML deserialize null elements?</a></p>
  
  <p>I've got elements like these from a third-party server for API testing:</p>
  
  <pre><code>&lt;Taxable /&gt;
  &lt;DefaultPurchasePrice /&gt;
  </code></pre>
  
  <p>I just realized that now I am confusing myself about whether elements like that represent null object or empty. </p>
  
  <p>Talking about objects, they are same, null object normally means empty object reference right? But trying to map a XML element to a datafield/value, they could be different i.e null string is empty string, but for Decimal price or Boolean value, they are undefined which equal to empty, but will not be null, unless they are defined as nullable. </p>
  
  <p>Again, the problem with my XmlSerializer is that wouldn't handle transfer an empty element like that. could I easily fix that in my code. Or should I ask people provide the XML have a well defined XML? Because seems that an empty XML element like that is undefined: it is here, but could be either null or empty doesn't matter for XML element itself? But for that element my code need figure out how to deal with that, unless I set all my C# class datafield as string type. Otherwise, if my code trying to directly map an empty or null XML element to a certain datafield, it will fail for sure.</p>
  
  <p>I have to ask this question because I encountered XML have lots of those elements
  and for those special elements, my .NET XMLserialization code need to mapped those field as string and if the string is not empty, I case them into correspondent datatype, otherwise I set them to null. And I end up remove those empty element before I do my deserialization because it is much easier. But I do wandering: "What am I really doing in my code? <strong>Did I just remove null elements or empty elements? Because they are clearly different!</strong> But people writing that XML think they are same, because XML itself don't have concept of 'null', and some people argue that it is my responsibility to decide whether it is null or empty. But XML do enable you to <a href="https://stackoverflow.com/questions/774192/what-is-the-correct-way-to-represent-null-xml-elements">represent 'null' elements in a clearer way</a></p>
  
  <p>Edit:</p>
  
  <p>In the example I presented, those two elements clearly should be null rather than empty elements. XML don't really have a concept of null, but those elements could either be omitted (if they are null, don't put them into XML) or using better representation as mentioned be @svick. Or in other cases, empty elements should be used when they make sense. But not for Decimal or Boolean. </p>