While my email was being looked around, i decided to keep looking for workaround and found one in an old post of WP7 developer forum
Here’s what you need to do.
If you are using Mango-specific features, you will need to add the following directory to your Settings –> User Defined Assembly Load Path (please use the correct Program Files directory based on your OS bitness).
- C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\Silverlight\v4.0\Profile\WindowsPhone71 (for 64-bit machines)
- C:\Program Files\Reference Assemblies\Microsoft\Framework\Silverlight\v4.0\Profile\WindowsPhone71 (for 32-bit machines)