. Net is a platform independent because mono organization found a framework to run in Linux, and it it is having clr, which is used for compiling ones and runs anywhere. It runs on any platform from windows95 to Linux. As you all know that in .net there are different compilers like for c#-csc,vb-vbc etc after your code is complied it will convert to MSIL code which is independent this MSIL code will goes to CLR & this CLR is platform dependent i.e. for Unix platform you should have Unix type of CLR ,for windows like the same so we can say that .net code is platform independent.
Now .Net becoming the Platform independent. A new Product called Mono, which is now developing by Novel that can support other platforms like Linux. One of strongest feature is that can support the local libraries like Linux GNOME Library.
Net is purely platform. Becuase it has got special features such as MSIL, CLR, JiT Compiler and more. What the source machine is, its language will be converted into Standard language, which is common to all called MS Intermediate language, by common language runtime (CLR). This MSIL will be converted into corresponding target machine language by Just-in-Time compiler. Hence .net is Purely platforms independent.
it is platform independent as well as platform dependent because dotnet will work on some other platforms also but it will not support linux so .net is paltformindependent as well as platform dependent.