title: Unsetting an enum flag
body: <p>Consider</p>
  
  <pre><code>   [Flags]
     public enum State
     {
        IsCool = 0x1,
        SomethingElse = 0x2
     }
  </code></pre>
  
  <p>I have a <code>State someState</code> and if some expression evaluates to true, I want to unset the <code>IsCool</code> flag of <code>someState</code> <em>regardless</em> of it being already set or unset. This means that I can't really use <code>someState ^= State.IsCool</code> but what can I use instead?</p>