title: Two-way binding in WPF
body: <p>I cannot get a two-way bind in WPF to work. </p>
  
  <p>I have a string property in my app's main window that is bound to a TextBox (I set the mode to "TwoWay"). </p>
  
  <p>The only time that the value of the TextBox will update is when the window initializes. </p>
  
  <p>When I type into the TextBox, the underlying string properties value does not change. </p>
  
  <p>When the string property's value is changed by an external source (an event on Click, for example, that just resets the TextBox's value), the change doesn't propagate up to the TextBox.</p>
  
  <p>What are the steps that I must implement to get two-way binding to work properly in even this almost trivial example?</p>