4.7. Native Image Generator

Native Image Generator (NGen is an application that can improve the startup performance of managed applications by carrying out the just-in-time (JIT) work normally done when the application is accessed. NGen creates processor-optimized machine code (images) of your application that are cached. This can reduce application startup time considerably.

Prior to .NET 4.0, if you updated the framework or installed certain patches, it was necessary to NGen your application all over again. But no longer; through a process known as targeted patching, regenerating images is no longer required.