CheckBox状态多选

前：

  <StackPanel Margin="10">
            <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;
        }