wpf combobox设置选中项背景颜色

今天刚好用到这个功能，记录下
博主写了个demo：https://github.com/xdqt/Wpf-datagrid-treeview.git

<ComboBox x:Name="combobox" ItemsSource="{Binding Grades}" SelectedItem="{Binding Kc}" IsEditable="True" Text="{Binding Edit}" LostFocus="Combobox_LostFocus">
            <ComboBox.Resources>
                <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}">Red</SolidColorBrush>
                <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}">Blue</SolidColorBrush>
            </ComboBox.Resources>
        </ComboBox>