Question

我已经在这个项目上工作了一个星期左右，在本周初，我的ReadFile返回了一个AccessViolationException - ＆＃34;试图读取或写入受保护的内存。＆＃34;所以我玩了一下它就消失了。我以为我修好了但也许没有？现在我的WriteFile正在抛出一个FatalExecutionEngineError，经过一些阅读后看来这两个事件可能是相关的;我不确定。以下是我的声明，可能存在以下问题：

    <DllImport("kernel32.dll")> Private Shared Function CloseHandle(
    ByVal hObject As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function CreateFile(
    <MarshalAs(UnmanagedType.LPStr)> ByVal lpFileName As String,
    ByVal dwDesiredAccess As Integer, ByVal dwShareMode As Integer,
    ByVal lpSecurityAttributes As Integer,
    ByVal dwCreationDisposition As Integer,
    ByVal dwFlagsAndAttributes As Integer,
    ByVal hTemplateFile As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function GetCommState(
    ByVal hCommDev As Integer, ByRef lpDCB As DCB) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function GetCommTimeouts(
    ByVal hFile As Integer, ByRef lpCommTimeouts As COMMTIMEOUTS) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function GetLastError() As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function PurgeComm(
    ByVal hFile As Integer, ByVal dwFlags As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function ReadFile(
    ByVal hFile As Integer, ByVal Buffer As Byte(),
    ByVal nNumberOfBytesToRead As Integer,
    ByRef lpNumberOfBytesRead As Integer,
    ByRef lpOverlapped As Overlapped) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetCommTimeouts(
    ByVal hFile As Integer, ByRef lpCommTimeouts As COMMTIMEOUTS) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetCommState(
    ByVal hCommDev As Integer, ByRef lpDCB As DCB) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function WriteFile(
    ByVal hFile As Integer, ByVal Buffer As Byte(),
    ByVal nNumberOfBytesToWrite As Integer,
    ByRef lpNumberOfBytesWritten As Integer,
    ByRef lpOverlapped As Overlapped) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetCommMask(
    ByVal hFile As Integer,
    ByVal dwEvtMask As Integer) As Integer
End Function

<DllImport("kernel32.dll", SetLastError:=True)> Private Shared Function WaitCommEvent(
    ByVal hFile As Integer,
    ByRef mask As Integer,
    ByRef lpOverlap As Overlapped) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function FormatMessage(
    ByVal dwFlags As Integer,
    ByVal lpSource As Integer,
    ByVal dwMessageId As Integer,
    ByVal dwLanguageId As Integer,
    ByVal lpBuffer As StringBuilder,
    ByVal nSize As Integer,
    ByVal Arguments As Integer) As Integer
End Function

这是最初导致AccessViolationException的代码，它已经消失了：

Private Function read() As String
    Dim sErrTxt As String
    Dim iReadChars, iRc As Integer

    If mhRS <> INVALID_HANDLE_VALUE Then
        ' Sets Comm Mask
        iRc = SetCommMask(mhRS, EventMasks.RxChar)
        If iRc <> 0 Then
            'Waits for a comm event
            iRc = WaitCommEvent(mhRS, miEvtMask, Nothing)
            If iRc <> 0 Then
                miStringSize = 0
                miString = ""
                ReDim mabtRxBuf(miBufferSize)
                ' Loop through the buffer and store it in a string while there is still chars in the buffer
                For i As Integer = 0 To 20
                    iRc = ReadFile(mhRS, mabtRxBuf, miBufferSize, iReadChars, Nothing)
                    If iRc <> 0 Then
                        ' Stores the size of the string read and forms the string
                        If iReadChars > 0 Then
                            miStringSize += iReadChars
                            miString &= defaultEncoding.GetString(mabtRxBuf)
                        End If
                    Else
                        ' Read Error 
                        sErrTxt = pErr2Text(GetLastError())
                        MsgBox("ReadFile failed " & sErrTxt)
                        Return Nothing
                    End If
                Next
                'Loop While iReadChars > 0
                ' Returns the concantenated string
                Return miString
            Else
                ' Handles WaitCommEvent error
                sErrTxt = pErr2Text(GetLastError())
                MsgBox("WaitCommEvent failed " & sErrTxt)
                Return Nothing
            End If
        Else
            ' Handles SetSommMask error
            sErrTxt = pErr2Text(GetLastError())
            MsgBox("Unable to SetCommMask " & sErrTxt)
            Return Nothing
        End If

    Else
        ' Handles port not open error
        MsgBox("Please initialize port first")
        Return Nothing
    End If
End Function

最后，这是导致FatalExecutionEngineError的代码：

Private Sub write(ByVal byteBuff As Byte())
    Dim sErrTxt As String
    Dim bytesSent = 0, iRc, iWriteChars As Integer

    If mhRS <> INVALID_HANDLE_VALUE Then
        ' Writes the passed Byte() to the comm port
        iRc = WriteFile(mhRS, byteBuff, byteBuff.Length, iWriteChars, Nothing)
        If iRc = 0 Then
            ' Handles WriteFile error
            sErrTxt = pErr2Text(GetLastError())
            MsgBox("WriteFile Failed " & sErrTxt)
        End If
    Else
        ' Handles port not open error
        MsgBox("Please initialize port first")
        Exit Sub
    End If
End Sub

我在Windows 7 64位上使用visual studio 2015和.NET 4.6.1。我重新安装了.net，它没有工作，所以我将应用程序转移到另一台机器上，看它是否可以在那里工作，但它没有。第二台机器与第一台机器相同。我不知道从哪里开始。

Answer 1

最终为我解决的代码：

        Private receivedText As String

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    With miPort
        .PortName = "COM3"
        .BaudRate = 38400
        .Parity = Parity.None
        .StopBits = StopBits.One
        .DataBits = 8
        .DtrEnable = True
        .RtsEnable = True
        .Handshake = Handshake.None
        .Encoding = Encoding.GetEncoding(28591)
    End With
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    If Not miPort.IsOpen Then
        miPort.Open()
    End If

    If miPort.IsOpen Then
        miPort.Write(toCharacters("55FF0510030004BC0105010189D1"))
    End If
End Sub

' Converts the passed string as hexidecimal numbers to its characters
Private Function toCharacters(ByVal hexText As String) As String
    Dim num As String
    Dim sendText As String = ""

    For y As Integer = 1 To Len(hexText) Step 2
        ' Takes two of the numbers passed (1 byte in Hex)
        num = Mid(hexText, y, 2)
        ' Converts the numbers into their decimal number, then to their character and stores them in a String()
        sendText &= (ChrW(Val("&h" & num)))
    Next y

    Return sendText
End Function

Private Sub miPort_DataReceived(sender As Object, e As SerialDataReceivedEventArgs) Handles miPort.DataReceived
    receivedText = miPort.ReadExisting()
End Sub

vb.net AccessViolationException和FatalExecutionEngineError

1 个答案: