PERWAPI is a module that reads and writes .NET program executable files. It was developed primarily as a file reader writer for programming language compilers. It defines classes for all of the features of the IL model, and methods to read and write the metadata of the PE-file. The module is written in C#, and does not rely on any facilities outside the base class libraries. It uses neither unmanaged code nor COM interop. In its current form it supports most of the features of the .NET V3.5 framework.Read more: Codeplex