title: Changing text of textblock from another page
body: <p>Messages.xaml</p>
  
  <pre><code>&lt;TextBlock  x:Name="txt_count_unreads" Text="0"  /&gt;
  </code></pre>
  
  <p>App.xaml
  check messages...and </p>
  
  <pre><code>Messages mm = new Messages();
  
   Messages.txt_count_unreads.Text = unreads.ToString();
  </code></pre>
  
  <p>But text not changing?What's wrong?</p>