When a user navigates through the suggestion list using the keyboard, you need to update the text in the text box to match.
You can set the TextMemberPath property to choose which property from your data object to display in the text box. If you specify a TextMemberPath, the text box is updated automatically. You should typically specify the same value for DisplayMemberPath and TextMemberPath so the text is the same in the suggestion list and the text box.
If you need to show more than a simple property, handle the SuggestionChosen event to populate the text box with custom text based on the selected item.