DLL 在 C# 中不起作用

Question

每当我尝试通过 Visual Studio 在 C# 中引用我自己的 DLL 时，它都会告诉我它无法引用 DLL，因为它不是 COM 库。

我在互联网上四处搜索以找到解决方案，但没有明确的答案或真正的帮助。这是一个相当“简单”的 DLL，它从指纹扫描仪捕获原始图片数据。在我尝试将其转换为 DLL 之前，我已经测试过 C++ 代码可以正常工作，你知道的。

我按照微软关于如何制作 DLL 的指南进行操作，结果如下：

• JTBioCaptureFuncsDll.h
• JTBioCaptureFuncsDll.cpp
• JTBioCapture.cpp

JTBioCaptureFuncsDll.h

#ifdef JTBIOCAPTUREFUNCSDLL_EXPORTS
#define JTBIOCAPTUREFUNCSDLL_API __declspec(dllexport)
#else
#define JTBIOCAPTUREFUNCSDLL_API __declspec(dllimport)
#endif

using byte = unsigned char*;

struct BioCaptureSample {
    INT32 Width;
    INT32 Height;
    INT32 PixelDepth;
    byte Buffer;
};

JTBioCaptureFuncsDll.cpp

// JTBioCapture.cpp : Defines the exported functions for the DLL application.
//

#include "stdafx.h"

namespace JTBioCapture
{
    using byte = unsigned char*;

    class JTBioCapture
    {
    public:
        // Returns a Struct with Information Regarding the Fingerprint Sample
        static JTBIOCAPTUREFUNCSDLL_API BioCaptureSample CaptureSample();
    };
}

JTBioCapture.cpp

/*
* Courtesy of WinBio God Satish Agrawal on Stackoverflow
*/
BioCaptureSample CaptureSample()
{
    HRESULT hr = S_OK;
    WINBIO_SESSION_HANDLE sessionHandle = NULL;
    WINBIO_UNIT_ID unitId = 0;
    WINBIO_REJECT_DETAIL rejectDetail = 0;
    PWINBIO_BIR sample = NULL;
    SIZE_T sampleSize = 0;

    // Connect to the system pool. 
    hr = WinBioOpenSession(
        WINBIO_TYPE_FINGERPRINT,    // Service provider
        WINBIO_POOL_SYSTEM,         // Pool type
        WINBIO_FLAG_RAW,            // Access: Capture raw data
        NULL,                       // Array of biometric unit IDs
        0,                          // Count of biometric unit IDs
        WINBIO_DB_DEFAULT,          // Default database
        &sessionHandle              // [out] Session handle
        );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioOpenSession failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }

    // Capture a biometric sample.
    wprintf_s(L"\n Calling WinBioCaptureSample - Swipe sensor...\n");
    hr = WinBioCaptureSample(
        sessionHandle,
        WINBIO_NO_PURPOSE_AVAILABLE,
        WINBIO_DATA_FLAG_RAW,
        &unitId,
        &sample,
        &sampleSize,
        &rejectDetail
        );
    if (FAILED(hr))
    {
        if (hr == WINBIO_E_BAD_CAPTURE)
        {
            wprintf_s(L"\n Bad capture; reason: %d\n", rejectDetail);
        }
        else
        {
            wprintf_s(L"\n WinBioCaptureSample failed. hr = 0x%x\n", hr);
        }
        goto e_Exit;
    }

    wprintf_s(L"\n Swipe processed - Unit ID: %d\n", unitId);
    wprintf_s(L"\n Captured %d bytes.\n", sampleSize);

    // Courtesy of Art "Messiah" Baker at Microsoft
    PWINBIO_BIR_HEADER BirHeader = (PWINBIO_BIR_HEADER)(((PBYTE)sample) + sample->HeaderBlock.Offset);
    PWINBIO_BDB_ANSI_381_HEADER AnsiBdbHeader = (PWINBIO_BDB_ANSI_381_HEADER)(((PBYTE)sample) + sample->StandardDataBlock.Offset);
    PWINBIO_BDB_ANSI_381_RECORD AnsiBdbRecord = (PWINBIO_BDB_ANSI_381_RECORD)(((PBYTE)AnsiBdbHeader) + sizeof(WINBIO_BDB_ANSI_381_HEADER));
    PBYTE firstPixel = (PBYTE)((PBYTE)AnsiBdbRecord) + sizeof(WINBIO_BDB_ANSI_381_RECORD);
    int width = AnsiBdbRecord->HorizontalLineLength;
    int height = AnsiBdbRecord->VerticalLineLength;

    wprintf_s(L"\n ID: %d\n", AnsiBdbHeader->ProductId.Owner);
    wprintf_s(L"\n Width: %d\n", AnsiBdbRecord->HorizontalLineLength);
    wprintf_s(L"\n Height: %d\n", AnsiBdbRecord->VerticalLineLength);

    BioCaptureSample returnSample;

    byte byteBuffer;
    for (int i = 0; i < AnsiBdbRecord->BlockLength; i++) {
        byteBuffer[i] = firstPixel[i];
    }
    returnSample.Buffer = byteBuffer;
    returnSample.Height = height;
    returnSample.Width = width;
    returnSample.PixelDepth = AnsiBdbHeader->PixelDepth;

    /*
    * NOTE: (width / 3) is necessary because we ask for a 24-bit BMP but is only provided
    * a greyscale image which is 8-bit. So we have to cut the bytes by a factor of 3.
    */
    // Commented out as we only need the Byte buffer. Comment it back in should you need to save a BMP of the fingerprint.
    // bool b = SaveBMP(firstPixel, (width / 3), height, AnsiBdbRecord->BlockLength, L"C:\\Users\\smf\\Desktop\\fingerprint.bmp");
    // wprintf_s(L"\n Success: %d\n", b);

e_Exit:
    if (sample != NULL)
    {
        WinBioFree(sample);
        sample = NULL;
    }

    if (sessionHandle != NULL)
    {
        WinBioCloseSession(sessionHandle);
        sessionHandle = NULL;
    }

    wprintf_s(L"\n Press any key to exit...");
    _getch();

    return returnSample;
}

这个想法是在 C# 中调用“CaptureSample()”，然后代码尝试捕获指纹扫描。当它进行扫描时，应该将一个结构返回给它可以使用的 C#，并持有：

• 字节缓冲区
• 图像高度
• 图像宽度
• 图像像素深度

但是当我尝试在我的 C# 项目中引用 DLL 时，我收到以下错误：

我也尝试使用TlbImp.exe 工具制作DLL，但无济于事。它告诉我 DLL 不是有效的类型库。

所以我在这里有点迷路了。我是 C++ 的新手，所以制作 Interop/COM 组件不是我以前做过的事情，也不是制作用于 C# 的 DLL。

Answer 1

您不能在 .NET 项目中引用用 C++ 编写的非托管代码库。 因此，要从此类库中调用代码，您必须使用DllImport，或使用WrapperClass。

我参考了这个答案：https://stackoverflow.com/a/574810/4546874。