official UE4 will support c # script?
You mean: Will UE4 officially support C# programming language?
And if that is what you mean, I unfortunately have to tell you that they almost certainly will not be.
Xamarin (the guys behind mono) were developing support for it, but unfortunately, it was pretty bulky, and they stopped working on it. You can still check it out here though:
Since UE4 uses C++ though, integration with any language is pretty easy. If you want to write the hard parts in managed code, like C#, you can still do that, and call into it by loading managed DLLs and loading functions from them. It might be a bit esoteric, but if you are a C++ programmer and just prefers C#, I’m sure you will be able to figure it out. My favourite library for making C# native exports is:
No IL hacks needed! The package does all the binary manipulation for you 
Best regards,
Temaran