I know there are many cases when it\'s best to multi thread an application but when is it best to multi thread a .net web Application?
In order to benefit from multithreading your application has to do a significant amount of work that can be run in parallel. If this is not the case, the overhead of multithreading may very well top the benefits.
In my experience most web applications consist of a number of short running methods, so apart from the parallelism already offered by the hosting environment, I would say that it is rare to benefit from multithreading within the individual parts of a web application. There are probably examples where it will offer a benefit, but my guess is that it isn't very common.