title: XML Serialization of Enums Without Default Values
body: <p>I have an enum: </p>
  
  <pre><code>[DataContract]
  public enum Relationship
  {
      Spouse = 4,
      ResidesWith = 1,
      Parent = 2,
      Other = 3,
      PersonalGuarantor = 5,
      CoApplicant = 6
  }
  </code></pre>
  
  <p>As you can see, zero is not defined.  I built my program around the idea that zero would never be defined in enums. That allows me to see which ones have been set from various comboBoxes, and which ones were set to a null value.  If I set zero as the null value, there is no way to tell those two things apart, and it essential that I be able to.  </p>
  
  <p>Due to the lack of a default state, I get an error when I try to serialize the values. </p>
  
  <p>Is there a way to have my xml serialize skip enums that have no value, or a way to avoid those errors?  I really do not want to introduce a default value. </p>