We have different web based products. All the products share same underlying authentication and authorization mechanism. All are on same database server and are ultimately published to same server.
Each project has its own namespace, folder structure and pages. Still due to the fact that authentication and authorization is shared, we use login and other pages across all the projects.
Also to make look and feel uniform across the projects/products we use same master pages.
Currently we have a separate project which contains code, markup and scripts etc. for shared things. We copy the markup and other things to all the projects to build and run them. It is really a hell. We have to include/exclude the files, change namespaces etc. all the times and over that make sure that shared things are at same version in all dependent projects.
What would be the best methodology to handle all this in a way that we don't go to asylum?
We are on ASP.Net 4.0, Visual Studio 2010, Telerik 2013 Q1 release.