title: Conditionally hide CommandField or ButtonField in Gridview
body: <p>I have a <code>GridView</code> displaying person records.  I want to conditionally show a <code>CommandField</code> or <code>ButtonField</code> based on some property of the underlying record. The idea is to only allow a command to be performed on specific people.</p>
  
  <p>What is the best way to do this? I'd prefer a declarative solution to a procedural one.</p>