I'm playing around with the C# reflection API. I can easily load
You can't with the reflection API (System.Reflection).
The reason is that the reflection api is designed to work on Metadata (Type of Classes, Name and Signature of Methods, ...) but not on the data level (which would be the IL-stream itself).
You can emit (but not read) IL with System.Reflection.Emit (e.g. ILGenerator Class).
MethodInfo.GetMethodBody() you can get the binary IL-stream for the implementation of a method. But thats usually completely useless by itself.
There are external libraries (like Cecil) that you can use to read/modify/add/delete code inside a method.