for the aspnet when you hit run, under (example 2.0):

C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files

you will find a folder per site. in the site there is temp folders for each
recycle, then a temp for each compile batch, page batch etc.

if you install the web deployment project, then you can do a deploy to a
known folder, where all the dll's will be built.

note: .net does not build object files, only dll's and exe's (which are
structured il files). most of the codedom routines no longer need to write a
source file to disk to compile it.

-- bruce (sqlwork.com)