title: check if a item in list, exists in another list with linq
body: <p>i'm new in c# ,sorry for bad question.</p>
  <p>how can i say, if an item in a list,</p>
  <p>exists in another list?</p>
  <p>l know it can be done using <strong>linq</strong> functions, but I don't know which method can help.</p>
  <p>I want something like this:</p>
  <pre><code>
  bool Exists(List&lt;int&gt; list1, List&lt;int&gt; list2)
  
  {
      // if the value of the first index of list1 exists in list2, return true.
  
  }
  
  </code></pre>