Is there any way to use xbmc plugins in .net? im thinking about those plugins that provide access to media content like GameTrailers and stuff like that..
I believe the plugin system is based on Python.  You may be able to use IronPython to run some of the plugins in XBMC, although it may not be 100% compatible.  You could also take the Python code and create a COM server object in which you could use .NET interop to interface with it.
Run XBMC plugins in a .net application