C++ to C#

I need to convert few of my C++ classes into C# is there any free software available or do you know any other way to accomplish it???

Why don't you just try compiling them as C++/CLI, with only slight modifications to make them managed? It might "just work", and then you could use those classes from C# as if they were written in C# itself.

Other than that, I don't think there are any automatic tools. Too complex. You'd have to do it by hand.