title: DataContext not updating (newbie question)
body: <p>I have an object called 'SelectedDay' I instantiate it like this: </p>
  
  <pre><code>Day SelectedDay = new Day(DateTime.Parse("01/01/0001"));
  </code></pre>
  
  <p>In Window_Loaded I set a listBox Datacontext to it:</p>
  
  <pre><code>lb_summary.DataContext = SelectedDay;
  </code></pre>
  
  <p>Later on in my app when a user clicks on a day in another ListBox, I pass it the new SelectedDay:</p>
  
  <pre><code>public void RefreshSummary(Day _selectedDay)
  {
      SelectedDay = _selectedDay;
  }
  </code></pre>
  
  <p>Im expecting lb_summary.DataContext to become _selectedDay but nothing happens, SelectedDay is the same as _selectedDay but the lb_summary.DataContext is empty.</p>
  
  <p>What am I missing?</p>
  
  <p><strong>EDIT</strong>:</p>
  
  <p>this is the object structure (they do implement INotifyPropertyChanged, edited to keep breif):</p>
  
  <pre><code>public class Day : INotifyPropertyChanged
  {       
      public string Title { get; set; }
      public DateTime DayDate { get; set; }
      public ObservableCollection&lt;Gig&gt; Gigs { get; set; }// gigs booked in a day_cell
  }
  
  public class Gig : INotifyPropertyChanged
  {
      // Properties of a gig
  }
  </code></pre>