Failed to load receiver assembly

This is a very common issue and it manifests in Visual Studio during deploy. For me, remedy was this:

1. Delete obj and bin folders of the solution.
2. Restart Visual Studio.
3. Set Always Force Install to true on all features.
4. Deploy.
5. Optionally, after successful deployment revert Always Force Install to false on all features.

More on the subject: https://sharepoint.stackexchange.com/questions/49612/failed-to-load-receiver-assembly-when-activate-feature