Ideally, we want access to fully template out Combobox and define custom visual states.

if not possible then at least being able to handle some of these design/use cases

Having a way to denote visually something is wrong or is an error

- red border  

- red underline

- red triangle in the corners

- text color change

Support for displaying images/icons in combobox (options)

- override the caret for dropdowns

- add images to left or right sides of combobox 

Technical Details:

- have a bool property to easily denote isError or something like isEnabled

- Error State Template and Styling property that can be fed a style object or Resource Dictionary Key

- Ability to trigger this thru xaml definition or c#