title: Linq, Lambda and nullable DateTime combination question
body: <h2>I have a Schedule class:</h2>
  
  <pre><code>public class Schedule
  {
  
   .....
  
   public DateTime? StartDate{get;set;}
   public DateTime? EndDate{get;set;}
  
   ....
  
  }
  </code></pre>
  
  <hr>
  
  <p>I would like to get the list of started Schedule objects from an IEnumerable list in the optimal way using <strong>linq</strong> or <strong>lambda</strong>.</p>
  
  <hr>
  
  <p><strong>NOTE:</strong> An empty date value means infinity here. However, unspecified schedule period (empty start and end dates) means schedule is not started ..</p>