Consider this property to be a switch that makes the FileChooser act like Dialog.OpenFile() instead of Dialog.SaveFile()

By default a FileChooser acts like Dialog.SaveFile() in the way that if you double click a file you will get a warning that the file already exists.

For loading files that already exist like you were using Dialog.OpenFile() you must set ReadOnly = True

This will however disable being able to type text in the lower TextBox of the FileChooser