/// The SCardGetStatusChange function blocks execution until the current availability of the cards in a specific set of readers changes.

static extern SCardFunctionReturnCodes SCardGetStatusChange(int hContext, int dwTimeout, [In, Out] SCARD_READERSTATE[] rgReaderStates, int cReaders);

  ret = SCardGetStatusChange(hContext, 100, rs, 1);

    internal static extern uint SCardGetStatusChange(IntPtr hContext, UInt32 dwTimeout, [In, Out] SCARD_READERSTATE[] rgReaderStates, UInt32 cReaders);

errorCode = SCardGetStatusChange(hContext, 0, readerState, nbReaders);