The Native Image Generator (Ngen.exe) is a tool that creates
native images, which are files containing compiled processor-specific machine
code, and installs them into the native image cache on the local computer. This
is an alternative to the JIT compiler. There are lots of changes to NGEN with
.NET Framework 2.0.
Installing an assembly also installs its dependencies,
simplifying the syntax of Ngen.exe.
Native images can now be shared across application domains.
New action, update, re-creates images that have been invalidated.
Actions can be deferred for execution by a service that uses idle
time on the computer to generate and install images.
Some causes of image invalidation have been eliminated.