按字母顺序对列表框中的项目进行分组

I have a WPF ListBox which shows a list of employees names. I want to group and sort them alphabetically. Is this possible? if so, how? Also, i will be required to style the headers (like the attached image) Could some1 guide me as to how i can achieve this. Thanx!I have a WPF ListBox which shows a list of empl