A proof-of-concept packer for .NET executables, designed to provide a starting point to explain the basic principles of runtime packing.
It is a full implementation of a simple .NET PE file packer, which doesn't use native code.

It can perform the following tasks:
pack itself
packing files packed by itself (up to four layers of packing are tested)
automagically resolve dependencies of the packed EXE

The following downsides/problems are known:
output files are quite big
there is no compression
console applications/DLLs cannot be packed.

The packer is implemented in a shared library called netcrypt.dll. If you reference this library you can just use the following code to pack a file:
byte[] arrayOfUnpackedExeBytes;
// ... perform file loading/generation logic
byte[] packedExe = Packer.Pack(arrayOfUnpackedExeBytes);