When I come across this problem I have search alot on net and then I found solution regarding the selectedValue selected in code behind when you have added item of the ComboBox within the xaml. We have used the Items Source property of the combo box and then bind the set the SelectedValue. Now solution for the problem  which I have mentioned is quite simple. For the sample test application I have two combo box one which is set normal and will not work is added first and then the second one which is work when setting the SelectedValue