thanks for your reply. I solve that propbem. as you said to me, I use that statement...like this.. int Get_Current_Media([MarshalAs(UnmanagedType.LPArray, SizeParamIndex=1)]out byte[]ar, out int len); My C++(dll) module can communicate with c# application perfectly...!!! but speed is so late. approximately spend 0.5 second. So I can't use this method in my c# application. I have a plan to remake application using c++ -_- Anyway I am really thankful to your answer.

neoksd wrote: Does anyone know a method to get and set textbox scrollbar positions? Off the top of my head you can P/Invoke GetScrollPos and SetScrollPos. I think you might be better to P/Invoke GetScrollInfo and SetScrollInfo instead though. - Nick Parker   My Blog