title: How to do null check for enum
body: <pre><code> public class myclass
      {
          public Details DetailsInfo { get; set; }
          public string name{ get; set; }
          public string Email { get; set; }
          public int subjects{ get; set; }
      }
  
  public enum subjects{
  maths,
  english,
  science,
  }
  </code></pre>
  
  <p>Among these subjects is an enum. Even if I don't enter any value for subjects it takes 0 by default. This is the behavior of enum. Is there any way to check if I have chose any value for subject.</p>
  
  <p>Note: I don't want to any value like undefined in the enum.</p>