Assuming the files you want to update are located in the application's
bin
directory, you can just copy the new files into the directory.
ASP.NET makes a "shadow copy" of the files, and loads them from the copy. When you update the files, it creates a new AppDomain to service any new requests, and signals the previous AppDomain to shut down as soon as it has finished servicing any current requests.
Shadow Copy and your \bin directory[
^]