Hello,
If you look at the XAML again you will see that the code for Disabled VisualState is only given for C1ComboBoxItem and not for C1ComboBox. I have got the Xaml style applied to C1ComboBox. Please go through the attached sample. I will discuss the issue with the concerned team to get to know the way to make override the disabled visual state for C1ComboBox.
Thanks,
Deepak Sharma