ASP.NET MVC5 each Razor Page very slow on first load

Question

This is not the same delay experiences when the first request arrives, but this is a delay that is experienced each time a Razor based view is accessed for the first ti

Answer 1

Webgrease. It minifies your production js and css bundles on first load, then caches them. Problem is that when the minification has errors it will try to compile every time, running whatever error routines are in there. There is no bug report and the only way of finding out this is happening is by directly opening the references and seeing stuff like:

/* Minification failed. Returning unminified contents.
(69,1): run-time error CSS1019: Unexpected token, found '@import'
(69,9): run-time error CSS1019: Unexpected token, found '"variables.less"'
(70,1): run-time error CSS1019: Unexpected token, found '@import'

Which (in the above case) reveals that your unnecessary .less or .sass files have been published - which is usually the result of wildcard bundling. Wildcard bundling will cost you more time than it saves.