Since xceed wpf toolkit doesnt work for me, I am trying to create a custom multi selection ComboBox using C# and WPF, by populating a ComboBox with Checkboxes and setting their width property so that the dropdown wont close, and using the Content property for the label.

I have a wpf app that runs in windows IoT with a touch screen. I have some screens with combo boxes which allow the user to press it and select an item and save it. The Combo boxes are put into a uniform grid so the combo box is quite large (for touch screen fingers). Everything seems to scale fine (text, dropdown items, the button), except the arrow. The graphic down arrow seems to always be the same size no matter what size the combo box is.

I’m trying to display a custom text on the header of a combobox, following the solution given here: