Why Does VS2010 “Lose” my reference on build?

Question

I\'ve developed a class library that does stuff, and tested it with unit tests. The library and tests build and work fine. I then added in a Windows Service project to the solut

Answer 1

Turns out, if you show the Warnings in the Build window, it tells you why :) Doh.

Service projects default to "Framework 4 Client Profile" now, and that is a sub-set of Framework 4 which means no linking to anything else other than that. Changed the project type to Framework 4 and all is good.

Answer 2

When there is a difference in Target .Net Framework(under project settings), it will create reference missing problems. It creates strange problems like when i add the reference it gets added. But when i build, again it will loose the reference. After making Target frame work same for both the project resolved the error.