I find dropdown list will be place at a wrong position when I change the text in the XamComboEditor. You can see it from wrong1.jpg in the zip file. I also attached my code to reproduce it.

1. build project and launch it.

2. move dialog to the bottom of screen.

3.  click in XamComboEditor and input 'a' to display the filter items.

4. the dropdown list will display far away from XamComboEditor

BTW, the forums become harder to insert image. Could you back to old style?