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I have a problem to pass a structure contained a structure pointer from to a C++ dll.
When i try the following code, this exception is raised :

In side i do :

Private Declare Function Cpp_NOR Lib "XLSTATLINK.dll" (<MarshalAs(UnmanagedType.Struct)> ByRef iData As ST_DataSet) As Double

    <StructLayout(LayoutKind.Sequential, Pack:=8)>
    Structure ST_DataSet
        'doubles1 data
        Public doubles1Loaded As Boolean
        Public doubles1 As ST_MVectDbl
    End Structure 

    <StructLayout(LayoutKind.Sequential, Pack:=8)>
    Structure ST_MVectDbl
        Public nbcols As Long 
        Public nbcolsreserved As Long 
        Public samenbrows As Boolean 
        Public nbrowsmax As Long 
        Public nbrows() As Long 
        Public vectors() As ST_VectDbl 
        Public cLabels() As String 
    End Structure

    <StructLayout(LayoutKind.Sequential, Pack:=8)>
    Structure ST_VectDbl
        Public count As Long 
        Public label As String 
        Public vect() As Double 
    End Structure

And in C++ code :

struct ST_DataSet
	//doubles1 data
	VARIANT_BOOL Doubles1Loaded;
	ST_MVectDbl Doubles1;

struct ST_MVectDbl
	int nbcols; 
	int nbcolsreserved; 
	VARIANT_BOOL samenbrows; 
	int nbrowsmax; 
	SAFEARRAY *nbrows; 
	ST_VectDbl *Vectors; 

struct ST_VectDbl
	int Count; 
	BSTR Label; 

XLSTATLINK_API double __stdcall Cpp_NOR(ST_DataSet *iData)


Anyone please can help me ?
Thanks in advance.
Updated 14-Oct-15 23:24pm
Richard MacCutchan 15-Oct-15 5:24am    
You need to catch the exception and check the details.
Member 10772496 15-Oct-15 5:27am    
How can i catch this exception ? And in which code side (C++ or should i do this ?
Richard MacCutchan 15-Oct-15 5:40am    
Use a Try/Catch block (or whatever VB.NET equivalent there is. And you catch it in the place that it gets thrown. Use your debugger first so you can quickly see what is going on.
Member 10772496 15-Oct-15 6:20am    
In debugger i have also the following exception :
Raised Exception  : 'System.Reflection.TargetInvocationException' dans mscorlib.dll
Richard MacCutchan 15-Oct-15 8:15am    
Sorry but that could mean anything.

1 solution

Don't kill yourself trying to become an expert at data marshaling when you don't need to be one.

Create a new VB.NET assembly (say "Types") and put all your data structures there.

Add a reference to this assembly in both the native and existing VB.NET projects.

Enable managed eg. C++/CLI in the native project.

Instead of ...

XLSTATLINK_API double __stdcall Cpp_NOR(ST_DataSet *iData)

... you can write something like ...

ref class CPP 
static double NOR(Types::ST_DataSet^ iData)
    if (iData->Doubles1Loaded) { ... }

    return 0.0;

From VB.NET you can call the above function using ...

dim iData as ST_DataSet


I'm not a VB.NET coder so I can't promise the VB.NET syntax is 100%.
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