Passing a Structure containing an array of String and an array of Integer into a C++ DLL
- by DanJunior
I'm having problems with marshaling in VB.NET to C++, here's the code :
In the C++ DLL :
struct APP_PARAM
{
int numData;
LPCSTR *text;
int *values;
};
int App::StartApp(APP_PARAM params)
{
for (int i = 0; i < numLines; i++)
{
OutputDebugString(params.text[i]);
}
}
In VB.NET :
<StructLayoutAttribute(LayoutKind.Sequential)> _
Public Structure APP_PARAM
Public numData As Integer
Public text As System.IntPtr
Public values As System.IntPtr
End Structure
Declare Function StartApp Lib "AppSupport.dll" (ByVal params As APP_PARAM) As Integer
Sub Main()
Dim params As APP_PARAM
params.numData = 3
Dim text As String() = {"A", "B", "C"}
Dim textHandle As GCHandle = GCHandle.Alloc(text)
params.text = GCHandle.ToIntPtr(textHandle)
Dim values As Integer() = {10, 20, 30}
Dim valuesHandle As GCHandle = GCHandle.Alloc(values)
params.values = GCHandle.ToIntPtr(heightHandle)
StartApp(params)
textHandle.Free()
valuesHandle.Free()
End Sub
I checked the C++ side, the output from the OutputDebugString is garbage, the text array contains random characters. What is the correct way to do this?
