title: Why doesn't HashTable.Contains() just simply return false if it is passed a null?
body: <p>I understand why passing a null to HashTable.Contains() doesn't work, but I don't understand what the point of it throwing an <code>ArgumentNullException</code> is - instead of just simply returning <code>false</code>? What is the benefit of throwing the exception (other than to make me do null checks before calling <code>.Contains()</code>)?</p>
  
  <blockquote>
    <p>Caused By [System.ArgumentNullException]<br>
    Key cannot be null.<br>
    Parameter name: key<br>
    at System.Collections.Hashtable.ContainsKey(Object key)<br>
    at System.Collections.Hashtable.Contains(Object key)  </p>
  </blockquote>