C# Signature:

    /// <summary>
    /// The SCardGetStatusChange function blocks execution until the current availability of the cards in a specific set of readers changes.
    /// </summary>
    /// <param name="hContext">A handle that identifies the resource manager context. The resource manager context is set by a previous call to the SCardEstablishContext function.</param>
    /// <param name="dwTimeout">The maximum amount of time, in milliseconds, to wait for an action. A value of zero causes the function to return immediately. A value of INFINITE causes this function never to time out.</param>
    /// <param name="rgReaderStates">An array of SCARD_READERSTATE structures that specify the readers to watch, and that receives the result.</param>
    /// <param name="cReaders">the number of elements in the rgReaderStates array.</param>
    /// <returns>This function returns different values depending on whether it succeeds or fails</returns>
[DllImport("winscard.dll", CharSet=CharSet.Auto)]
static extern SCardFunctionReturnCodes SCardGetStatusChange(int hContext, int dwTimeout, [In, Out] SCARD_READERSTATE[] rgReaderStates, int cReaders);

User-Defined Types:

    public enum SCardFunctionReturnCodes : uint
    {
    SCARD_S_SUCCESS = 0x0,
    //'Errors
    SCARD_E_CANCELLED =         0x80100002,
    SCARD_E_INVALID_HANDLE =        0x80100003,
    SCARD_E_INVALID_PARAMETER =     0x80100004,
    SCARD_E_INVALID_TARGET =        0x80100005,
    SCARD_E_NO_MEMORY =         0x80100006,
    SCARD_F_WAITED_TOO_LONG =       0x80100007,
    SCARD_E_INSUFFICIENT_BUFFER =       0x80100008,
    SCARD_E_UNKNOWN_READER =        0x80100009,
    SCARD_E_TIMEOUT =           0x8010000A,
    SCARD_E_SHARING_VIOLATION =     0x8010000B,
    SCARD_E_NO_SMARTCARD =          0x8010000C,
    SCARD_E_UNKNOWN_CARD =          0x8010000D,
    SCARD_E_CANT_DISPOSE =          0x8010000E,
    SCARD_E_PROTO_MISMATCH =        0x8010000F,
    SCARD_E_NOT_READY =         0x80100010,
    SCARD_E_INVALID_VALUE =         0x80100011,
    SCARD_E_SYSTEM_CANCELLED =      0x80100012,
    SCARD_E_INVALID_ATR =           0x80100015,
    SCARD_E_NOT_TRANSACTED =        0x80100016,
    SCARD_E_READER_UNAVAILABLE =    0x80100017,
    SCARD_E_PCI_TOO_SMALL =         0x80100019,
    SCARD_E_READER_UNSUPPORTED =    0x8010001A,
    SCARD_E_DUPLICATE_READER =      0x8010001B,
    SCARD_E_CARD_UNSUPPORTED =      0x8010001C,
    SCARD_E_NO_SERVICE =        0x8010001D,
    SCARD_E_SERVICE_STOPPED =       0x8010001E,
    SCARD_E_UNEXPECTED =        0x8010001F,
    SCARD_E_ICC_INSTALLATION =      0x80100020,
    SCARD_E_ICC_CREATEORDER =       0x80100021,
    SCARD_E_DIR_NOT_FOUND =         0x80100023,
    SCARD_E_FILE_NOT_FOUND =        0x80100024,
    SCARD_E_NO_DIR =            0x80100025,
    SCARD_E_NO_FILE =           0x80100026,
    SCARD_E_NO_ACCESS =         0x80100027,
    SCARD_E_WRITE_TOO_MANY =        0x80100028,
    SCARD_E_BAD_SEEK =          0x80100029,
    SCARD_E_INVALID_CHV =           0x8010002A,
    SCARD_E_UNKNOWN_RES_MNG =       0x8010002B,
    SCARD_E_NO_SUCH_CERTIFICATE =       0x8010002C,
    SCARD_E_CERTIFICATE_UNAVAILABLE =   0x8010002D,
    SCARD_E_NO_READERS_AVAILABLE =      0x8010002E,
    SCARD_E_COMM_DATA_LOST =        0x8010002F,
    SCARD_E_NO_KEY_CONTAINER =      0x80100030,
    SCARD_E_SERVER_TOO_BUSY =       0x80100031,
    SCARD_E_UNSUPPORTED_FEATURE =       0x8010001F,
    //'The F...not sure
    SCARD_F_INTERNAL_ERROR =        0x80100001,
    SCARD_F_COMM_ERROR =        0x80100013,
    SCARD_F_UNKNOWN_ERROR =         0x80100014,
    //'The W...not sure
    SCARD_W_UNSUPPORTED_CARD =      0x80100065,
    SCARD_W_UNRESPONSIVE_CARD =     0x80100066,
    SCARD_W_UNPOWERED_CARD =        0x80100067,
    SCARD_W_RESET_CARD =        0x80100068,
    SCARD_W_REMOVED_CARD =          0x80100069,
    SCARD_W_SECURITY_VIOLATION =    0x8010006A,
    SCARD_W_WRONG_CHV =         0x8010006B,
    SCARD_W_CHV_BLOCKED =           0x8010006C,
    SCARD_W_EOF =               0x8010006D,
    SCARD_W_CANCELLED_BY_USER =     0x8010006E,
    SCARD_W_CARD_NOT_AUTHENTICATED =    0x8010006F,
    SCARD_W_INSERTED_CARD =         0x8010006A,
    }

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

private const int SCARD_STATE_UNAWARE = 0x00000000;

// get ATR of card
// hContext - previously established context
// reader - ATR will be read from card in this reader
private static byte[] atr(int hContext, string reader)
{
  int ret;
  byte[] atr = null;
  SCARD_READERSTATE[] rs = new SCARD_READERSTATE[1];
  rs[0].szReader = reader;
  rs[0].dwCurrentState = SCARD_STATE_UNAWARE;

  ret = SCardGetStatusChange(hContext, 100, rs, 1);
  if (ret == 0 && rs[0].cbAtr > 0 && rs[0].rgbAtr != null)
  {
   atr = new byte[rs[0].cbAtr];
   Array.Copy(rs[0].rgbAtr, atr, rs[0].cbAtr);
  }
  return atr;
}

Alternative Managed API:

TODO