title: WPF DataContext updated but UI not updated
body: <p>I have maximum simple app. I want to fill listbox when button pressed. I use binding, window DataContext is updated after some operation, but UI not updated!</p>
  
  <p>Here is the code:</p>
  
  <p><strong>MainWindow.xaml</strong></p>
  
  <pre><code>&lt;Window x:Class="WpfApplication1.MainWindow"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="MainWindow" Height="350" Width="525"&gt;
  &lt;Grid&gt;
      &lt;Button Content="Button" HorizontalAlignment="Left" Margin="432,288.04,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/&gt;
      &lt;ListBox x:Name="urlsListBox" ItemsSource="{Binding Urls}" HorizontalAlignment="Left" Height="300" Margin="10,10,0,0" VerticalAlignment="Top" Width="417"/&gt;
  
  &lt;/Grid&gt;
  </code></pre>
  
  <p></p>
  
  <p><strong>MainWindow.xaml.cs</strong></p>
  
  <pre><code>    namespace WpfApplication1
  {
  
      public partial class MainWindow : Window
      {
          ViewModel model = new ViewModel();
  
          public MainWindow()
          {
              InitializeComponent();
              this.DataContext = model;
          }
  
          private void Button_Click(object sender, RoutedEventArgs e)
          {
              model.GetUrls();
          }
      }
  }
  </code></pre>
  
  <p><strong>ViewModel.cs</strong></p>
  
  <pre><code>    namespace WpfApplication1
  {
      class ViewModel
      {
          private ObservableCollection&lt;Url&gt; Urls { get; set; }
  
          public ViewModel()
          {
              Urls = new ObservableCollection&lt;Url&gt;();
          }
  
          public void GetUrls()
          {
              for (int i = 0; i &lt; 5; i++)
              {
                  Urls.Add(new Url { link = i.ToString() });
              }
          }
      }
  
      public class Url
      {
          public string link { get; set; }
      }
  }
  </code></pre>