title: DataBinding RadioButton IsSelected only works once
body: <p>I have a problem with data binding. I am using MVVM Light.</p>
  
  <p>When I set a breakpoint on the setter of one of the bools in my view model and select the corresponding radio button, the debugger halts and all looks fine.</p>
  
  <p>Then when I continue, select the other radio button and select the first radio button again, the debugger is not halting. What is going wrong?</p>
  
  <p>I have two two radiobuttons:</p>
  
  <pre><code>            &lt;RadioButton  Margin="5" Grid.Row="1" Content="Browser cookies" GroupName="loginmethod" IsChecked="{Binding IsBrowserCookiesChecked}"/&gt;
              &lt;RadioButton  Margin="5" Grid.Row="2" Content="Username + password" GroupName="loginmethod" IsChecked="{Binding IsUsernamePasswordChecked}"/&gt;
  </code></pre>
  
  <p>I have bounded them to two separate bools in my view model which looks as follows:</p>
  
  <pre><code>   public const string IsUsernamePasswordCheckedPropertyName = "IsUsernamePasswordChecked";
  
      private bool _isUsernamePasswordChecked = false;
      public bool IsUsernamePasswordChecked
      {
          get
          {
              return _isUsernamePasswordChecked;
          }
  
          set
          {
              if (_isUsernamePasswordChecked == value)
              {
                  return;
              }
  
              RaisePropertyChanging(IsUsernamePasswordCheckedPropertyName);
              _isUsernamePasswordChecked = value;
              RaisePropertyChanged(IsUsernamePasswordCheckedPropertyName);
          }
      }
  
      public const string IsBrowserCookiesCheckedPropertyName = "IsBrowserCookiesChecked";
  
      private bool _isBrowserCookiesChecked = true;
  
      public bool IsBrowserCookiesChecked    
      {
          get
          {
              return _isBrowserCookiesChecked;
          }
  
          set
          {
              if (_isBrowserCookiesChecked == value)
              {
                  return;
              }
  
              RaisePropertyChanging(IsBrowserCookiesCheckedPropertyName);
              _isBrowserCookiesChecked = value;
              RaisePropertyChanged(IsBrowserCookiesCheckedPropertyName);
          }
      }
  </code></pre>