title: Check IEnumerable<T> is filled with optional words not to count
body: <p>I am trying to create extension isEmpty method which would check whether my IEnumerable contains at least one element. Returning either true/false.
  I would like to also be able to exclude some specific items from check therefore it should be like this:</p>
  
  <p><strong>1st check:</strong> if <code>list</code> items count == 0 then return true</p>
  
  <p><strong>2nd check:</strong> If not <code>list</code> empty (count > 0) then check what elements are there. If i say for instance in parameter <code>listSpecialItems</code> that i want: string.empty, "whatever", "dd" then if <code>list</code> contains only those items it should still return true. Means <code>listSpecialItems</code> defines items as they would not exist (not counts).</p>
  
  <p>This is so far what i did, however at the moment it only checks items count.</p>
  
  <pre><code>public static bool IsEmpty&lt;T&gt;(this IEnumerable&lt;T&gt; list, IEnumerable&lt;T&gt; listSpecialItems)
  {
       if (list is ICollection&lt;T&gt;) return ((ICollection&lt;T&gt;)list).Count == 0;
           return !list.Any();
  }
  </code></pre>