title: How can I detect "missing" elements in an IEnumerable<T>?
body: <p>I've got an <code>IEnumerable&lt;T&gt;</code> containing a list of data elements with consistent intervals in one of the properties:</p>
  
  <pre><code>List&lt;Interval&gt; list = new List&lt;Interval&gt;
              { 
                  new Interval{ TIME_KEY = 600},
                  new Interval{ TIME_KEY = 605},
                  new Interval{ TIME_KEY = 615},
                  new Interval{ TIME_KEY = 620},
                  new Interval{ TIME_KEY = 630}
              };
  </code></pre>
  
  <p>How can I query this list (using Linq, preferably), to get a List that looks like this:</p>
  
  <pre><code> List&lt;Interval&gt; list = new List&lt;Interval&gt;
                  { 
                      new Interval{ TIME_KEY = 610},
                      new Interval{ TIME_KEY = 625}
                  };
  </code></pre>
  
  <p>?</p>
  
  <p>EDIT: I will probably know what the interval distance is supposed to be, but if there's a way to determine it by examing the data, that would be a huge bonus!</p>
  
  <p>EDIT: changed to numeric values</p>