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POConvert Visual Basic 6.0 type to VB.NET 'Structure'
 

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  1. POConvert Visual Basic 6.0 type to VB.NET 'Structure'
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    <p>EDIT: Having gotten this to work under 32-bit, I'm now trying to get it to work for 64-bit. I've gotten source code for the DLL and both DLL and application are being compiled for 64-bit. I get an access violation every time. Here is the DLL code (C++ in <a href="http://en.wikipedia.org/wiki/Microsoft_Visual_Studio#Visual_Studio_2005" rel="nofollow">Visual&nbsp;Studio&nbsp;2005</a>):</p> <pre><code>#pragma pack( push, 2 ) // Output Results Structure typedef struct tagTVA_RESULTS { int iID; /* Difference ID 1 .. n */ int iLeft; /* Bounding rectangle */ int iRight; int iTop; int iBottom; double dCx; /* Center of gravity */ double dCy; double dMajor; /* Shape information */ double dMinor; double dAngle; /* Rotational information */ int lArea; /* Number of pixels */ int iEdge; /* Set if difference is at the edge of the image */ double dNormalDensity; int iNormalCount; double dDifferenceDensity; } TVA_RESULTS, *PTVA_RESULTS; #pragma pack ( pop ) </code></pre> <p>Note it's setting the pack to 2. I've tried setting it to 2 in the application as well, and it fails. I tried other values, and I even tried values that weren't the same. I've tried explicit using 4 as integer size and 8 as double size. But I would assume (with limited knowledge) that if both pack sizes are the same, it should work.</p> <p>At this point I'm suspecting how the function is called. Its first parameter is a pointer to an array of these structures. The application passes in the first element of the array ByRef, which I think accomplishes this. But having a bad pointer to the array would explain the symptoms. Here's the function definition in the DLL.</p> <pre><code>int WINAPI MNtvaAnalyzeVB (TVA_RESULTS *pResults, int iMaxCount) </code></pre> <p>My boss suggested it could be an <a href="https://en.wikipedia.org/wiki/Endianness" rel="nofollow">big/little endian</a> problem, but that seems unlikely if they're both being compiled in the same environment.</p> <p>What should I do?</p> <blockquote> <blockquote> <blockquote> <p>End of edit >>></p> </blockquote> </blockquote> </blockquote> <hr/> <p>I am converting a Visual Basic 6.0 application to VB.NET. I have a couple of structures that get passed to external DLL files. This is not working, and I have a feeling it's due to the structures not being passed correctly.</p> <p>Here's the original structure:</p> <pre><code>Public Type TVA_PARAMETERS iStandardFilterOnOff As Long iSampleFilterOnOff As Long iDifferenceFilterOnOff As Long iRotationCorrectionOnOff As Long iLocalCorrectionOnOff As Long iStandardAOIx As Long iStandardAOIy As Long iStandardAOIdx As Long iStandardAOIdy As Long iSampleAOIx As Long iSampleAOIy As Long iSampleAOIdx As Long iSampleAOIdy As Long iRepeatHorizontal As Long iRepeatVertical As Long dSensitivity As Double iMergeWidth As Long iMergeHeight As Long iMinimumDifferenceArea As Long iMaximumDifferenceArea As Long End Type </code></pre> <p>If I do a LenB on a variable of that type in Visual Basic 6.0, I get 84 bytes. (N.B.: I'm not sure if that's a valid way to determine its size.)</p> <p>I have tried to convert it to VB.NET thusly:</p> <pre><code>Public Structure TVA_PARAMETERS Public iStandardFilterOnOff As Integer Public iSampleFilterOnOff As Integer Public iDifferenceFilterOnOff As Integer Public iRotationCorrectionOnOff As Integer Public iLocalCorrectionOnOff As Integer Public iStandardAOIx As Integer Public iStandardAOIy As Integer Public iStandardAOIdx As Integer Public iStandardAOIdy As Integer Public iSampleAOIx As Integer Public iSampleAOIy As Integer Public iSampleAOIdx As Integer Public iSampleAOIdy As Integer Public iRepeatHorizontal As Integer Public iRepeatVertical As Integer Public dSensitivity As Double Public iMergeWidth As Integer Public iMergeHeight As Integer Public iMinimumDifferenceArea As Integer Public iMaximumDifferenceArea As Integer End Structure </code></pre> <p>In VB.NET, <a href="https://msdn.microsoft.com/en-us/library/vstudio/system.runtime.interopservices.marshal.sizeof%28v=vs.100%29.aspx" rel="nofollow">System.Runtime.InteropServices.Marshal.sizeof()</a> gives 88 bytes. I was hoping since these are just numeric values this would work (I know strings can be a pain). I don't have code for the external function, but it's declared like this:</p> <pre><code>Declare Function MNtvaParameters Lib "MNTva.dll" (ByRef pParameters As TVA_PARAMETERS) As Integer </code></pre> <p>I'm guessing this structure is not the same size, so the DLL file call fails, but I get no error, and as I said, I don't have the code to look it. It returns a zero, as is should if it's successful, but it's clearly not actually having an effect.</p> <p>I've played around a bit with <a href="https://msdn.microsoft.com/en-us/library/vstudio/system.runtime.interopservices.structlayoutattribute%28v=vs.100%29.aspx" rel="nofollow">Runtime.InteropServices.StructLayoutAttribute</a>, but if that's the answer, I cannot determine the right parameters.</p> <p>I have another structure like this, but it's so similar. I'm guessing if I can fix this one, I'll be able to fix the other.</p>
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    1. USPeter Mortensen
    1. USDan Barron
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    1. COI have no idea what this question is about, but it looks cool, so +1. :)
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      1. USNeolisk
    2. CO@Neolisk: It is probably the "I have a couple of structures that get passed to external DLLs. This is not working".
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      1. USPeter Mortensen
 

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