c# - C# WinScard.SCardListReaders 应该只列出连接的阅读器（但它列出了所有过去安装的现在未连接的阅读器名称）

Question

请浏览我下面的 C# 代码。我正在尝试获取现在连接到我的计算机的智能卡读卡器列表。但是这个函数会返回过去连接的所有智能卡读卡器名称（我的意思是现在没有连接）。我只想要活动（当前）连接的读者名称列表。我无法理解问题出在哪里。

我尝试了这个网站上的一个 exe，它是用 C 编写和编译的。它只显示连接的读者。我比较了代码，但我发现没有区别。请帮助找到解决方法。

public static int GetPCSCReaders(out List<string> smartCardReaders, out string errMsg)
{
    errMsg = string.Empty;
    byte[] readersList = null;
    smartCardReaders = new List<string>();

    try
    {
        int hContext = 0;
        int ret = SCardEstablishContext(WinSCard.SCARD_SCOPE_USER, 0, 0, ref hContext);
        if (ret != 0)
        {
            errMsg = "WinSCard GetPCSCReader: EstablishContext Error: " + ret.ToString();
            return ret;
        }

        int byteCnt = 0;
        ret = WinSCard.SCardListReaders(hContext, null, null, ref byteCnt);
        if (ret != SCARD_S_SUCCESS)
        {
            errMsg = "WinSCard GetPCSCReader: ListReaders Error: " + ret.ToString();
            return ret;
        }

        readersList = new byte[byteCnt];
        ret = WinSCard.SCardListReaders(hContext, null, readersList, ref byteCnt);
        if (ret != SCARD_S_SUCCESS)
        {
            errMsg = "WinSCard GetPCSCReader: ListReaders Error: " + ret.ToString();
            return ret;
        }

        int indx = 0;
        string readerName = string.Empty;
        int i = 0;

        while (readersList[indx] != 0)
        {
            while (readersList[indx] != 0)
            {
                readerName = readerName + (char)readersList[indx++];
            }

            smartCardReaders.Add(readerName);
            i++;

            readerName = "";
            indx++;
        }

    }
    catch (Exception ex)
    {
        errMsg = ex.Message;
    }
    finally
    {
        readersList = null;
    }
    return 0;
}

score 1 · Accepted Answer

我浏览了这个链接，在那个页面中，有一个提示和技巧提到，“如果您调用 SCardListReaders 并将 hContext 参数设置为 null，您将获得已安装阅读器的列表（而不是插入的阅读器！）”。据此，在我的代码中，我将 hContext 变量设置为 int，我将其更改为 IntPtr，它让我只列出连接的阅读器。它已解决，现在我的代码更改为

public static int GetPCSCReaders(out List<string> smartCardReaders, out string errMsg)
{
    errMsg = string.Empty;
    smartCardReaders = new List<string>();
    IntPtr hContext;

    try
    {
        int ret = SCardEstablishContext(SCARD_SCOPE_USER, IntPtr.Zero, IntPtr.Zero, out hContext);
        if (ret != SCARD_S_SUCCESS)
        {
            errMsg = "WinSCard GetPCSCReader: EstablishContext Error: " + ret.ToString();
            return ret;
        }

        byte[] readersList = null;
        uint byteCnt = 0;
        ret = SCardListReaders(hContext, null, null, ref byteCnt);
        if (ret != SCARD_S_SUCCESS)
        {
            errMsg = "WinSCard GetPCSCReader: ListReaders Error: " + ret.ToString();
            return ret;
        }

        readersList = new byte[byteCnt];
        ret = SCardListReaders(hContext, null, readersList, ref byteCnt);
        if (ret != SCARD_S_SUCCESS)
        {
            errMsg = "WinSCard GetPCSCReader: ListReaders Error: " + ret.ToString();
            return ret;
        }

        int indx = 0;
        string readerName = string.Empty;
        int i = 0;

        while (readersList[indx] != 0)
        {
            while (readersList[indx] != 0)
            {
                readerName = readerName + (char)readersList[indx++];
            }

            smartCardReaders.Add(readerName);
            i++;

            readerName = "";
            indx++;
        }

    }
    catch (Exception ex)
    {
        errMsg = ex.Message;
    }
    finally
    {

    }
    return 0;
}