TFS 2010 mapping dependent files for builds

I am pretty new to TFS and Build configuration tasks so forgive me if this problem has a simple answer.

I have a team project that is sort of a common library(CL) that contains dlls and apis that I commonly use throughout my projects. All my other projects reference files directly from the mapped folder for the CL on my dev machine.

I am trying to set up a build definition for Project A(Build server is on a different machine). I want always ensure that the CL is the latest before each build so is it possible to have the build definition pull the latest files first? The only other alternative is to start including the CL in of every p开发者_开发知识库roject directly.

I tried adding a working folder for the CL, but it does not seem to get the files before it attempts to build project A. And then after when I try to rebuild after the failure, I receive a error saying that the CL working folder "is already mapped in workspace".

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Instead of mapping in the sources, why not build the common library, deploy it to a common location, and have all the projects that use it reference it at the common location?

In addition to simply making more sense (it should be common binary, not common source), this greatly improves Continuous Integration builds. If several builds map the same source into their workspace, then when the common source is changed, all of those CI builds will be kicked off.