Posted by & filed under IDE.

As my previous post shows I recently installed MVC 4 on my development machine.  I ran into an annoying gotcha by doing this.

I have an MVC 3 app that I maintain and I needed to make a small change to a previous version of the app in our test environment.  I should have been pretty straight forward. I branched my in progress changes, updated to the version in test, made the change and rebuilt the app.  Then I pushed the new dlls to the server, assuming everything would work.

To my surprise I was getting exceptions in previously working code.  Turns out the MVC 4 install updated the System.Web.Helpers dll in the GAC.  This caused my project to now have a dependency on this new version.  The fix was pretty straight forward, I just set the “copy local” flag in the project reference, rebuilt and pushed that dll to server.  I also need to update the web.config to reflect the dependency on this version.

<add assembly="System.Web.Helpers, Version=, Culture=neutral" />