Zip files in C#

Question

Hello,
I am trying to figure out a way of opening standard .zip files in C#. I know of possiblilities of using third party libraries such as SharpZipLib and cross language solutions like using J# libaries but neither of those solutions work for me. I do not want to use third party solutions at all and using the J# librairies makes it difficult to write the zip files to a memorystream.
I also have heard of using the windows API to get the job done but does anyone know of a solution staying solely in C#? Or at lease a simple way of using the API, I am not good with API calls at all. All I need to do is unzip contents into a memory stream. There is no manipulation of the zip file or rezipping anything at all.
Please help!!