There is no way to diable the echo information in pure C# :(. you have to call CRT API getch, it will not display input information. It is said MS will support more functionalities of Console in next version.
[DllImport("msvcrt.dll", EntryPoint="_getch")]
public extern static int getch();
If you want to open another command window(start another process), you can call createprocess API(in kernal32.dll)