scardtransmit返回空的接收字节数组

Question

我正在研究一个c# PC/SC实现与ACS阅读器和NFC标签。

我已经制作了SCardTransmit的原型如下:

[DllImport("winscard.dll")]
public static extern int SCardTransmit (Int32 hCard, ref SCARD_IO_REQUEST pioSendRequest, byte[] SendBuff, Int32 SendBuffLen, ref SCARD_IO_REQUEST pioRecvRequest, byte[] RecvBuff, out Int32 RecvBuffLen);

我有以下代码:

        SCard.SCARD_IO_REQUEST ioRequest = new SCard.SCARD_IO_REQUEST();
        ioRequest.dwProtocol = Protocol; // Is going to be T=1
        ioRequest.cbPciLength = 8;
        byte[] cmdBytes = new byte[] { 0xFF, 0xCA, 0x00, 0x00, 0x00 };
        byte[] rcvBytes = new byte[10];
        int rcvLenght = 0;
        retCode = SCard.SCardTransmit(Handle,
            ref ioRequest, cmdBytes, cmdBytes.Length,
            ref ioRequest, rcvBytes, out rcvLenght);
        if (retCode != SCard.SCARD_S_SUCCESS)
            throw new Exception("Failed querying tag UID: " + retCode);

所有(未显示)初始化的东西似乎工作正常，我可以成功地获得标签的ATR。

现在，运行这段代码，我得到一个成功的返回代码，我收到一个一致的接收字节长度值，但相应的字节数组是空的(0)。

有谁能给点建议吗?

谢谢。

Answer 1

SCardTransmit的原型最有可能是问题所在。我将把它写成:

[DllImport("winscard.dll")]
public static extern uint SCardTransmit(Int32 hCard, SCARD_IO_REQUEST pioSendPci, [In] byte[] pbSendBuffer, uint cbSendLength, SCARD_IO_REQUEST pioRecvPci, [In, Out] byte[] pbRecvBuffer, ref uint pcbRecvLength);

主要区别在于倒数第二个参数pbRecvBuffer，它用属性In和Out声明。