title: How can I make a Button appear in the Header of a WPF TabItem using bindings?
body: <p>I am creating a UI in which a <code>TabControl</code> has a series of standard <code>TabItem</code>s with ordinary WPF controls as their content. The headers just display ordinary strings as usual. However, I want the header of the last item to contain a <code>Button</code> instead of an ordinary string.</p>
  
  <p>Let me stress that <strong>I already know how to do this without bindings. I want to do it with bindings.</strong> Specifically, the <code>TabControl</code> is bound to an array of <code>UserControl</code>s, except for the last object which is a <code>Button</code>. It is this <code>Button</code> that I want to appear in the header instead of as the content of the last <code>TabItem</code>. (I frankly don't care what the content of the last <code>TabItem</code> is. Only the header.)</p>
  
  <p>I understand <code>DataTemplateSelector</code>s and <code>StyleSelector</code>s. What I can't figure out is what combination of styles and templates will do this for me. <strong>Specifically, I need to know what the <code>Style</code> and <code>DataTemplate</code> for the last item should look like, so that I can select them appropriately. No other code need be shown.</strong></p>