Are Windows Phone 8.0 DLLs compatible with Windows Phone 8.1 apps?

Question

I have a Windows Phone 8.1 project, and a Windows Phone 8.0 library. I need to add it into my Windows Phone 8.1 project; but at runtime, I have the following error:

FileNotFoundException: could not load or assembly Microsoft.Phone, Version=8.0.0.0. The system cannot find the file specified.

So my question is simple: are 8.0 libs compatible with Windows Phone 8.1 app ? If not, what should I do ? Migrate them ?

Answer 1

If your project is Windows Phone 8.1 Silverlight, that it should work fine. If your project is Windows Phone 8.1 XAML (which seems more probable according to the error message) , then no, no way to use it without rewriting.