anchor.diff:      to the literal string of the template expression.
     code-example(format="." ).
       [(x)]="hero.name" &lt;==> [x]="hero.name" (xChange)="hero.name=$event"
  +    
  +  :marked
  +    We can write a two-way binding directive of our own to exploit this behavior.
   
   :marked
     Is `[(ngModel)]` all we need? Is there ever a reason to fall back to its expanded form?
   
  -  The `[( )]` syntax can only set the data-bound property when the value changes.
  +  The `[( )]` syntax can only _set_ a data-bound property.
     If we need to do something more or something different, we need to write the expanded form ourselves.
   
     Let's try something silly like forcing the input value to uppercase:
  
positive.code:   :marked
      The `ngModel` input property sets the element's value property and the `ngModelChange` output property 
      listens for changes to the element's value.
      The details are specific to each kind of element and therefore the `NgModel` directive only works for elements
      that implement one of a few patterns such as the input box's `value` property and `change` event. 
      We can't simply apply `[(ngModel)]` to our custom components unless we write them to conform.
      
  :marked
    That’s an improvement, but it could be better.
  
    We shouldn't have to mention the data property twice. Angular should be able to read the component’s data property and set it
    with a single declaration &mdash; which it can with the `[( )]` syntax:
  // #enddocregion ngModel-5
  +makeExample('template-syntax/ts/app/app.component.html', 'NgModel-1')(format=".")
  
negative.code: :marked
    There’s a story behind this construction, a story that builds on the property and event binding techniques we learned previously.
  
    ### Inside [(ngModel)]
    We could have achieved the same result with separate bindings to
    the `<input>` element's  `value` property and `input` event.
  // #enddocregion ngModel-3
  +makeExample('template-syntax/ts/app/app.component.html', 'without-NgModel')(format=".")
  