MultiSelectComboBox

多项选择下拉菜单
https://github.com/xceedsoftware/wpftoolkit/wiki/CheckComboBox

https://github.com/guruyuvan/WpfMultiSelectCombobox

https://github.com/sdl/Multiselect-ComboBox

https://blog.csdn.net/wqy_zyc/article/details/79566506
https://files.cnblogs.com/files/waleswood/MultiSelectComboBox_Demo_MVVM_.zip