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October 21st, 2012, 02:29 PM
#1
AccessViolationException on API Call
Hi,
I migrated a VB6 ActiveX to Vb.Net and I am having an issue on API Calls.
The ActiveX consist of making API calls to read or write data from flat files.
It works pretty well in VB6, but throws an exception in Vb.Net : AccessViolationException
Let me know if you want me to post the working VB6 Code
Also, I apologize for my english skills. =)
Here is the VB.Net Code:
Code:
Module nif_types
'Define structure for RGETDAT_BITS procedure call
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Ansi)> _
Public Structure rgetdat_bits_data_str
Dim type As Short 'data type (set internally)
Dim file As Short 'file in database
Dim rec As Short 'record in file
Dim word As Short 'word offset in record
Dim start_bit As Short 'start bit in word
Dim length As Short 'number of bits
Dim flags As Short 'flags
Dim padding As Short
Dim value As Short 'database value
<VBFixedArray(2)> Dim padV() As Short
Dim status As Short 'return status
<VBFixedArray(2)> Dim padA() As Short
Public Sub Initialize()
ReDim padV(2)
ReDim padA(2)
End Sub
End Structure
End Module
Module HSCNAPI
Public Declare Function rgetdat_bits Lib "hscnetapi.dll" Alias "rgetdat_bits_vb" (ByVal Server As String, ByVal num_points As Short, ByRef getdat_bits_data() As rgetdat_bits_data_str) As Short
End Module
Class MyControl
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=255)> Dim ServerName As String ' For fixed length compatibility
Public Sub GetServerName()
ServerName = RegQuery("Honeywell", "Experion PKS Server", "Server", "ConnectedServerName")
End Sub
Public Function HSC_get_bits_data(ByVal iFile As Short, ByVal iRec As Short, ByVal iWord As Short, ByVal iStart As Short, Optional ByVal DataNumber As Integer = 1) As Array
Dim ArrData(0) As rgetdat_bits_data_str
Dim ArrReturn(0 To 100) As String
Dim iWordCount As Integer = 0
Dim iBitCount As Integer = 0
Try
For i As Integer = 0 To DataNumber - 1
ArrData(0).file = (iFile)
ArrData(0).rec = Convert.ToInt16(iRec)
ArrData(0).word = Convert.ToInt16(iWord + iWordCount)
ArrData(0).start_bit = Convert.ToInt16(iStart + iBitCount)
ArrData(0).length = Convert.ToInt16(1)
ArrData(0).flags = Convert.ToInt16(0)
rgetdat_bits(ServerName, Convert.ToInt16(1), ArrData) ' <------------------- Stacktrace shows this Exception happens on this line, which is the API Call
ArrReturn(i) = CStr(ArrData(0).value)
iBitCount += 1 ' Counter to increment the StartBit by 1: 1 bit = 1 bit.
If iBitCount = 16 Then ' 0 to 15 represent 16 bits. When 16 bit count is reached, increment word and reset bit counter
iWordCount += 1
iBitCount = 0
End If
Next
Return ArrReturn
Catch Ex1 As AccessViolationException
'mylogWriter.WriteLine("Record Time: " & time.ToString(timeformat) & " :: " & "HSC_get_bits_data: " & Ex1.Message, Ex1.InnerException.ToString)
Catch Ex As Exception
'mylogWriter.WriteLine("Record Time: " & time.ToString(timeformat) & " :: " & "HSC_get_bits_data: " & Ex.Message, Ex.InnerException.ToString)
End Try
Return Nothing
End Function
End Class
Thanks
Alex
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October 23rd, 2012, 02:19 AM
#2
Re: AccessViolationException on API Call
I think we'll need to see the working Structure in the VB6 side of things...
Sure it's a probably a bad structure problem...
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