Hello,
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Is it possible to add a filter in a ComboBox?
There is no native API in ComboBox that could add a filter in the ComboBox. My suggestion is that you could create a custom control which contains a ComboBox and other controls like Buttons, CheckBoxes, and ListView to show a filter list.
In the custom control, there is a button on right of the ComboBox, then the button is clicked, a Listview contains the keywords for filter and CheckBox in each row. When some keywords are checked, you could filter the itemsource of the ComboBox according to the keywords and show the filtered list in the ComboBox
Besides, I have another suggestion here. Is AutosuggestBox acceptable for you? I noticed that you mentioned you want the customer only to choose. But it is complicated to create a custom control and handle all the logic by yourself. AutoSuggestBox will make suggestions to users as they enter text. You could check the input and show the result as you want by handling TextChanged Event and SuggestionChosen Event.
Thank you.