title: Lazy loading WPF tab content
body: <p>My WPF application is organized as a TabControl with each tab containing a different screen.</p>
  
  <p>One TabItem is bound to data that takes a little while to load. Since this TabItem represents a screen that users may only rarely use, I would like to not load the data until the user selects the tab.</p>
  
  <p>How can I do this?</p>