Mono.Cecil.Inject (Cecil.Inject from now on) is a simple library that adds a few convenience methods to the original Mono.Cecil library. Added functionality includes method injection, System.Reflection-style methods to search other methods and class members by name and parameters and fast accessibility modification.
The library is almost a seamless addition to Mono.Cecil that should've been in the original library from the beginnig. The library is compact, easy-to-use and well documented.
Online documentation (along with a library overview) can be found here.
If you have used ReiPatcherPlus before, you can grab the migration guide from Migration directory.
To build from source, you will need the latest version of MSBuild that is capable of compiling C# 6 source code and Mono.Cecil.
Simply place Mono.Cecil.dll into lib folder and run build.bat or use MSBuild.