Problem:
I have both VS 2008 and 2010 on my Win 7 PC, and have used VS 2008 and SQL Server 2008R2 for Exercise 4 - Use Methods from a Custom Assembly on p.514 of the TK-448 book, but I got the error as in the title.
Solution:
Copy the .dll file to the right place as below:
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\PrivateAssemblies
(not the one in C:\Program Files\...........)