title: Why is NaN (not a number) only available for doubles?
body: <p>I have a business class that contains two nullable decimal properties. A third property returns the result of multiplying the other two properties. If HasValue is true for the two nullable types then I multiply and return the result. I have a few options for the return value if one or both of the properties is null:</p>
  
  <ul>
  <li>Return 0</li>
  <li>Throw an exception</li>
  <li>Return a magic number (-1)</li>
  <li>Return decimal? (EDIT -- see comments)</li>
  </ul>
  
  <p>I thought one of my options would be to return NaN, but I see that this is only possible for the double type. Why is this?</p>
  
  <p>For the record, returning 0 makes the most sense in this case and that's what I plan to do unless someone has a better suggestion.</p>