<CheckBox x:Name="checkBoxMergeAudio" IsChecked="{Binding IsMergeAudio, Mode=TwoWay}" Margin="0,0,0,0" Click="checkBoxMergeAudio_Changed" ClickMode="Release">
     <TextBlock TextWrapping="Wrap" Text="{Binding LocalizedResources.MergeAudio, Source={StaticResource LocalizedStrings}}" />
</CheckBox>

and in the code behind:

private void checkBoxMergeAudio_Changed(object sender, RoutedEventArgs e) {
  //save the changed state of the checkbox
  Utility.SetAppSettings(Constants.MergeAudio, (((SettingsPivotDataSource)DataContext).IsMergeAudio).ToString());
}

Note that using the TextBox style of the CheckBox, I succeded to handle also the possible wrapping of the text field of that control.

 <StackPanel Margin="0,0,0,0" Grid.Row="0" Background="{StaticResource BrushTransparentGray}">
                        <RadioButton Content="{Binding LocalizedResources.AlwaysLogin, Source={StaticResource LocalizedStrings}}" Name="alwaysLoginButton" IsChecked="{Binding LoginType, Converter={StaticResource EqualityConverter}, ConverterParameter=0, Mode=OneWay}" GroupName="AutoLoginGroup" Click="alwaysLoginButton_Checked" ClickMode="Release"  />
                        <RadioButton Content="{Binding LocalizedResources.DailyLogin, Source={StaticResource LocalizedStrings}}" Name="daylyLoginButton" IsChecked="{Binding LoginType, Converter={StaticResource EqualityConverter}, ConverterParameter=1, Mode=OneWay}"  GroupName="AutoLoginGroup" Click="daylyLoginButton_Checked" ClickMode="Release" />
                        <RadioButton Content="{Binding LocalizedResources.TimeStampLogin, Source={StaticResource LocalizedStrings}}" Name="loginEveryButton" IsChecked="{Binding LoginType, Converter={StaticResource EqualityConverter}, ConverterParameter=2, Mode=OneWay}" GroupName="AutoLoginGroup" Click="loginEveryButton_Checked" ClickMode="Release" />
</StackPanel>

and in the code behind:

 private void alwaysLoginButton_Checked(object sender, RoutedEventArgs e) {
            LoginTypeWrapper actualLoginTypeWrapper = new LoginTypeWrapper(LoginType.ALWAYS);
            if (!DataSourceManager.SettingsPivotDataSource.LoginType.Equals(actualLoginTypeWrapper)) {
                DataSourceManager.SettingsPivotDataSource.LoginType = actualLoginTypeWrapper;
                //salvo la nuova impostazione scelta dall'utente
                Utility.SetAppSettings(Constants.LoginType, LoginType.ALWAYS.ToString());
            }
        }

        private void daylyLoginButton_Checked(object sender, RoutedEventArgs e) {
            LoginTypeWrapper actualLoginTypeWrapper = new LoginTypeWrapper(LoginType.DAILY);
            if (!DataSourceManager.SettingsPivotDataSource.LoginType.Equals(actualLoginTypeWrapper)) {
                DataSourceManager.SettingsPivotDataSource.LoginType = actualLoginTypeWrapper;
                //salvo la nuova impostazione scelta dall'utente
                Utility.SetAppSettings(Constants.LoginType, LoginType.DAILY.ToString());
            }
        }

        private void loginEveryButton_Checked(object sender, RoutedEventArgs e) {
            LoginTypeWrapper actualLoginTypeWrapper = new LoginTypeWrapper(LoginType.EVERY);
            if (!DataSourceManager.SettingsPivotDataSource.LoginType.Equals(actualLoginTypeWrapper)) {
                DataSourceManager.SettingsPivotDataSource.LoginType = actualLoginTypeWrapper;
                //salvo la nuova impostazione scelta dall'utente
                Utility.SetAppSettings(Constants.LoginType, LoginType.EVERY.ToString());
            }
        }

where the converter is the following:

    public class EqualityConverter : IValueConverter {

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
           if (parameter != null && value is LoginTypeWrapper) {
                if (((LoginTypeWrapper)value).Code == System.Convert.ToInt32(parameter)) {
                    return true;
                }
            }
            return false;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
            throw new NotImplementedException();
        }
    }