I need to create quite a lot of urlrewrite-rules to catch different urlrewriting scenarioes. So I began defining the rules in urlrewriting.config but it slowed down my site considerably, so I decided to write my own rewriting provider and create a dictionary with exact matches on the incoming URLs and cache the dictionary.This solution seems to be really fast compared to my previous regex-rules in urlrewriting.config.

I would like to build the dictionary on application start, so I inherited from ApplicationBase. The problem is, that at this point the umbracocontext is not available and I need the niceUrl of some nodes to put in the dictionary. I also tried fetching the nodes as documents directly from the DB and use the umbraco.library.NiceUrl. None of these work because the umbracocontext is not available yet. 

For testing purposes I tried creating a page with a button, which would call the exact same code to build the dictionary. This works perfectly because the umbracocontext has been created at this point. But I need the code to run on application start.

I then tried creating the UmbracoContext in my code on application start, but then I get the following exception:

"The current httpContext can only be set once during a request"

So my question is, how can I call a method right after umbracocontext has been loaded?

thanks

Thomas