Here is another scenario where you might confront this error. If you rename your project so that the file name of the assembly changes, it’s possible for you to have two versions of your ASP.NET assembly, which will reproduce this error.
The solution is to go to your bin
folder and delete the old dlls. (I tried “Rebuild Project”, but that didn’t delete ’em, so do make sure to check bin
to ensure they’re gone)