Doesn't work for Windows Phone 8.1 XAML

I am developing windows phone 8.1. app. and I have implemented adrotator for wp8.1
it gives an error Like:
Cannot find type System.Windows.Controls.UserControl in module System.Windows.dll.

Here is you can view my question on stackoverflow. http://stackoverflow.com/questions/29161240/adrotator-in-windows-phone-8-1-xaml

[thalescm]

The same is happening for me. But this is happening when I add the AdMob reference.

[SimonDarksideJ]

Hmm, we tested thoroughly with the Universal / 8.1 solution. We have an update upcoming, we shall reverify and test again

[SimonDarksideJ]

Looks like it's an issue with AdMob, they still haven't updated their control to 8.1 standards.
Sadly it looks they used some functionality that was not forwards compatible with 8.1, locking them in to 8.0. It also appears they have no interest in Windows advertising going forward :(

Will keep digging to see if I can find a workaround. For now, you'll have to use other providers like Smaato and such on 8.1.