Protecting .NET dlls and licencing

I am little concerned about protecting my dlls from being reverse engineered. Want to know liitle more about the topic.

It seems that .Net dll can be deassembled to reveal all the protected information. I want to licence my product, and thought that creating an encrypted licence file, with private key stored in resource of exe, or dll, or some constant. But i am concerned if some one can simply deassemble my dll, or even use in its own project, and access the private key to write the licence...

i am not interested in buying third party fuscators, is there any better approaches to achieve this... all i want is that my private and critical information must stay hidden one way or the other...

Thanks...