CheckBox状态多选

前：

   <StackPanel Margin="">
             <Label FontWeight="Bold">Application Options</Label>
             <StackPanel Margin="10,5">
                 <CheckBox IsThreeState="True" Name="cbAllFeatures" Checked="cbAllFeatures_CheckedChanged" Unchecked="cbAllFeatures_CheckedChanged">Enable all</CheckBox>
                 <StackPanel Margin="20,5">
                     <CheckBox Name="cbFeatureAbc" Checked="cbFeature_CheckedChanged" Unchecked="cbFeature_CheckedChanged">Enable feature ABC</CheckBox>
                     <CheckBox Name="cbFeatureXyz" IsChecked="True" Checked="cbFeature_CheckedChanged" Unchecked="cbFeature_CheckedChanged">Enable feature XYZ</CheckBox>
                     <CheckBox Name="cbFeatureWww" Checked="cbFeature_CheckedChanged" Unchecked="cbFeature_CheckedChanged">Enable feature WWW</CheckBox>
                 </StackPanel>
             </StackPanel>
         </StackPanel>

         private void cbAllFeatures_CheckedChanged(object sender, RoutedEventArgs e)
         {
             bool newVal = (cbAllFeatures.IsChecked == true);
             cbFeatureAbc.IsChecked = newVal;
             cbFeatureXyz.IsChecked = newVal;
             cbFeatureWww.IsChecked = newVal;
         }

         private void cbFeature_CheckedChanged(object sender, RoutedEventArgs e)
         {
             cbAllFeatures.IsChecked = null;
             if ((cbFeatureAbc.IsChecked == true) && (cbFeatureXyz.IsChecked == true) && (cbFeatureWww.IsChecked == true))
                 cbAllFeatures.IsChecked = true;
             if ((cbFeatureAbc.IsChecked == false) && (cbFeatureXyz.IsChecked == false) && (cbFeatureWww.IsChecked == false))
                 cbAllFeatures.IsChecked = false;
         }