title: RadioButton IsChecked loses binding
body: <p>I'm triying to bind to a RadioButton.IsChecked property, and it only works once. After that, the binding doesn't work anyore, and I have no idea why this happens. Can anyone help out with this? Thanks!</p>
  
  <p>This is my code.</p>
  
  <p>C#</p>
  
  <pre><code>public partial class Window1 : Window
  {
      public Window1()
      {
          InitializeComponent();
  
          this.DataContext = new ViewModel();
      }
  }
  
  public class ViewModel
  {
      private bool _isChecked1 = true;
      public bool IsChecked1
      {
          get { return _isChecked1; }
          set
          {
              if (_isChecked1 != value)
              {
                  _isChecked1 = value;
              }
          }
      }
  
      private bool _isChecked2;
      public bool IsChecked2
      {
          get { return _isChecked2; }
          set
          {
              if (_isChecked2 != value)
              {
                  _isChecked2 = value;
              }
          }
      }
  }
  </code></pre>
  
  <p>XAML:</p>
  
  <pre><code>&lt;Grid&gt;
      &lt;StackPanel&gt;
          &lt;RadioButton Content="RadioButton1" IsChecked="{Binding IsChecked1}" /&gt;
          &lt;RadioButton Content="RadioButton2" IsChecked="{Binding IsChecked2}" /&gt;
      &lt;/StackPanel&gt;
  &lt;/Grid&gt;
  </code></pre>