Monday, 28 July 2014

SharePoint Virtual Directory Mapping Mayhem

I had updated a 2010 VS solution which contained references to a custom CSS file and several image resources. Upon deploying it to my 2013 farm I was surprised to see that all these links were broken.

All my references used the traditional tilde followed by "/_layouts/" and then the end path - i.e. ˜\_layouts\SolutionFolder\myfile.ext - which looked just fine and matched the same format I've always used. In addition, the deployment location for Layouts and Images directory within VS was using the {SharePointRoot} token and correctly placing everything within its correct location on the server.

So I changed the URL in the open browser window to point to a few OOTB application pages and images and noticed hit and miss results with these too! What was going on??

I carefully checked and compared file permissions, toyed with different file formats and extensions... There was no pattern to this madness!

I dug a little deeper and noticed that the files which were successfully loading also existed in the 14 directory. Hmmm... This led me to take a look at the virtual directory mappings in IIS and this is what I found:

The _layouts virtual directory actually maps to SharePoint 2010’s 14 hive!

One can only assume that this was done for backwards compatibility with 2010 solutions, which can also be deployed to the same farm.

Lesson learnt. Always include the hive version in the path when referencing server-side resources.

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