.net code injection

.NET Internals and Code Injection

http://www.ntcore.com/files/netint_injection.htm

Windows Hooks in the .NET Framework

http://msdn.microsoft.com/en-us/magazine/cc188966.aspx#S6

Rewrite MSIL Code on the Fly with the .NET Framework Profiling API

http://msdn.microsoft.com/en-us/magazine/cc188743.aspx

CLR Injection: Runtime Method Replacer

http://www.codeproject.com/Articles/37549/CLR-Injection-Runtime-Method-Replacer

.NET Framework Rootkits: Backdoors inside your
Framework

http://www.sans.org/reading_room/whitepapers/windowsnet/dotnet-framework-rootkits-backdoors-framework_32954