public static extern Boolean TwAddVarCB( [In] IntPtr bar, [In, MarshalAs(UnmanagedType.LPStr)] String name, [In] Tw.VariableType type, [In] Tw.SetVarCallback setCallback, [In] Tw.GetVarCallback getCallback, [In] IntPtr clientData, [In, MarshalAs(UnmanagedType.LPStr)] String def);