title: force property implementation on derived classes
body: <p>I have <code>Person.cs</code> which will be implemented by, for example, the <code>Player</code> class. 
  <code>Person</code> has an <code>ExperienceLevelType</code> property. </p>
  
  <p>I want to force all classes that derived from <code>Person</code> to implement their own version of the <code>ExperienceLevelType</code> property.</p>
  
  <pre><code>public abstract Person
  {
      public enum ExperienceLevel { Kid, Teenager}
      public virtual ExperienceLevel Experience {get; set;}
  }
  
  public abstract Player:Person
  {
      public override ExperienceLevel Experience
      {
  
      }
  }
  </code></pre>