static extern int MsiSetInternalUI(INSTALLUILEVEL dwUILevel, ref IntPtr phWnd);
public static extern UInt32 MsiSetInternalUI(INSTALLUILEVEL dwUILevel, ref IntPtr phWnd);
[DllImport("msi", CharSet = CharSet.Auto)] // UI level // handle of owner window public static extern INSTALLUILEVEL MsiSetInternalUI(INSTALLUILEVEL dwUILevel, ref IntPtr winhandle);