Breeze / Knockout下拉列表导致实体被修改

This is a bit of an odd issue I came across today. I have an application that is using Breeze and Knockout. On one of my pages I allow the user to edit and save project data. The save button is only enabled if a change has been made. To track changes I subscribe to the propertyChanged event. This page has quite a few dropdowns which are causing some problems. Here is an example of one of the dropdowns. This is a bit of an odd issue I came across tod