title: How to center a text field on iOS?
body: <p>I am having trouble using constraints to center a text field both vertically and horizontally.</p>
  
  <p>I have a tabbed iPhone application project open in Visual Studio Community 2015. The project is restricted to portrait mode only, so no landscape to worry about.</p>
  
  <p>How do I center a text field in a <code>UIViewController</code> both vertically and horizontally, so that when I re-size my screen (iPhone 6 screen size to 5s screen size) it stays centered?</p>