VB6 到 VB.NET 转换问题，对 .dll 函数的函数调用返回错误

Question

我最近将 VB6 程序转换为 VB.NET。该程序用于与Superlogics PCM系列DAQ卡进行通信，该卡已不再生产，并且不支持VB.NET。我的程序在 VB6 中运行良好，但在 VB.net 中由于外部 .dll 文件中的功能而出现问题（虽然我不确定），

我阅读了很多论坛并对编组属性做了一些更改。所以，请大家给我解决这个问题的想法 -

错误

'我收到 intStatus = 350 的错误（指“无效请求句柄”）

'The superlogics手册只是要求我检查PCMDigitalInputVB函数。请帮助我，提前致谢

Public Function singleDigitalInput(ByVal LogicalDevice As Short, ByVal Channel As Short, ByRef InputValue As Byte) As Long

    Dim intStatus As Short
    Dim intRequestHandle As Short
    Dim udtDigioRequest As New DigioRequest
    udtDigioRequest.Initialize()
    Dim udtDataBuffer As New PCMDriveBuffer
    Dim udtAllocateRequest As New allocate_request

    Dim lngRetChannelAdd As Integer
    Dim lngRetBufferAdd As Integer

    Dim blnCompleteStatus As Boolean
    Dim lngEventMask As Integer
    Dim ErrorCode As Short

    On Error GoTo errUnknown



    intRequestHandle = 0
    blnCompleteStatus = False

    '-------------------------------------------------------------------
    'Allocate and lock memory for the Digital Input
    '-------------------------------------------------------------------

    With udtAllocateRequest
        .request_type = DIGIN_TYPE_REQUEST
        .channel_array_length = 1
        .number_of_buffers = 1
        .buffer_size = 1
        .buffer_attributes = RING_BUFFER
    End With

    intStatus = PCMAllocateRequestVB(LogicalDevice, udtAllocateRequest)

    If intStatus <> 0 Then
        singleDigitalInput = intStatus
        Exit Function
    End If

    'Debug.Print "Allocate Request Status = " & intStatus

    '-------------------------------------------------------------------
    'Prepare the Digital Input Request Structure
    '-------------------------------------------------------------------

    lngRetChannelAdd = PCMGetAddressOfVB(Channel)
    'UPGRADE_WARNING: Couldn't resolve default property of object udtDataBuffer. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="6A50421D-15FE-4896-8A1B-2EC21E9037B2"'
    lngRetBufferAdd = PCMGetAddressOfVB(udtDataBuffer)

    With udtDigioRequest
        .ChannelArrayPtr = lngRetChannelAdd
        .ArrayLength = 1
        .DigioBufferptr = lngRetBufferAdd
        .NumberOfScans = 1
        .IOMode = ForegroundCPU
        .TriggerSource = InternalTrigger
        .ScanEventLevel = 0
        .RequestStatus = NoEvents
    End With

    '-------------------------------------------------------------------
    'Send a digital input request to the PCMDrive

'我收到一条错误消息，指出“Invalid Request Handle”，intStatus = 350

'superlogics 手册要求我检查 PCMDigitalInputVB 函数，仅此而已 '------------------------------------------------- ------------------

    intStatus = PCMDigitalInputVB(LogicalDevice, udtDigioRequest, intRequestHandle)


End Function

'-----函数声明'----------------

Declare Function PCMDigitalInputVB Lib "PCMDrvVB.DLL" (ByVal logical_device As Short, ByRef Request As DigioRequest, ByRef handle As Short) As Short

'-------- ----- 结构声明----------------------------------------

Structure DigioRequest
    Dim ChannelArrayPtr As Integer ' address of channel scan list
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray0 As Short() ' reserved for future expansion
    Dim ArrayLength As Short ' length of chan & gain arrays
    Dim DigioBufferptr As Integer ' address of PCMDRIVE_buffer
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray1 As Short() ' reserved for future expansion
    Dim TriggerSource As Short ' trigger source
    Dim TriggerMode As Short ' continuous / one-shot trigger
    Dim TriggerSlope As Short ' rising / falling edge trigger
    Dim TriggerChannel As Short ' trigger channel number
    '   (analog or digital trigger)
    Dim TriggerVoltage As Double ' trigger voltage (analog trigger)
    Dim TriggerValue As Integer ' value for trigger (digital trigger)
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray2 As Short() ' reserved for future expansion
    Dim IOMode As Short ' input mode
    '    = 0 poll
    '    = 1 IRQ
    '    = 2 DMA with CPU status
    '    = 3 DMA with IRQ status
    Dim ClockSource As Short ' clock source (0 = internal)
    Dim ClockRate As Double ' clock rate (if not internal)
    Dim SampleRate As Double ' input sampling rate (Hz)
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray3 As Short() ' reserved for future expansion
    Dim NumberOfScans As Integer ' number of channel scans
    Dim ScanEventLevel As Integer ' generate event each scan_event_level
    '    scans ( 0 = disable )
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=7)> Dim ReservedArray4 As Short() ' reserved for future expansion
    Dim TimeoutInterval As Short ' timeout interval (in sec)
    Dim RequestStatus As Integer ' request event status
    Public Sub Initialize()
        ReDim ReservedArray0(3)
        ReDim ReservedArray1(3)
        ReDim ReservedArray2(3)
        ReDim ReservedArray3(3)
        ReDim ReservedArray4(7)
    End Sub
End Structure

Answer 1

由于 VB6 代码工作正常，我只需将相关接口代码转换（包装）到 VB6 类模块中并创建一个 COM 组件（新建项目 > ActiveX DLL in VB6）。
可以使用 COM Interop 从 .NET 调用生成的 COM DLL。
另请参阅这个问题了解更多详细信息。

Answer 2

这看起来像是 pInvoke 问题。这些可能会非常令人沮丧。正如前面的评论者所说，将现有代码包装到 VB6 COM 组件中并从 dotNet 项目中调用它可能会更容易。

不过，从 dotNet 上也应该可以实现。要记住的一件事是垃圾收集器。垃圾收集器可以随时将任何变量（包括 UDT/结构）移动到内存中。通常，这会表现为应用程序有时工作，但有时不工作。

如果每次都发生错误，请仔细检查 API 调用的 pInvoke 声明，并确保使用正确的数据类型和大小。还要确保您正确地通过val/byref 传递参数。

除此之外，如果不访问 API 文档或进行大量试验和错误，就很难诊断这些问题。