title: Reading an IEnumerable multiple times
body: <p>Let's say I have some code:</p>
  
  <pre><code>var items = ItemsGetter.GetAllItems().Where(x =&gt; x.SomeProperty &gt; 20);
  int sum1 = items.Sum(x =&gt; x.SomeFlag == true);
  </code></pre>
  
  <p>And for example I need some other sum from the items collection later in the code.</p>
  
  <pre><code>int sum2 = items.Sum(x =&gt; x.OtherFlag == false);
  </code></pre>
  
  <p>So my question: Is it OK to call Linq methods on <code>IEnumerable</code> more than once? Maybe I should call <code>Reset()</code> method on enumerator or make list from items using <code>ToList</code> method?</p>