C# Custom Marshalling or Managed C++ wrapper.

Vikas Sirigiri

I have a C++ Component class being written in a DLL and a DLL export funtion that returns the pointer to the Component Class.

class Component
{
    char* name;
    char* id;
    char* version;
    char* description;
    Component* parent;
    std::list children;
}

DLLEXPORT Component* Enumerate()
{
return Module::GetInstance();
}

In my C# Application, in order to access the Component class using the Enumerate funtion, do I need to use managed C++/CLI wrapper or use

Marshal.PtrtoStructure or ICustomMarshalling

What is the correct way to do this?

3 Replies

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Bechir Bejaoui17y ago
Accepted answer
Marshal.PtrToStructure is the best one but remain one issue is that the caller code must be trusted, so you have to apply security persmissions to protect the solution from being miss used be mallisious untrusted code
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Bechir Bejaoui17y ago
http://support.microsoft.com/?scid=kb%3Ben-us%3B871182&x=9&y=9
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Vikas Sirigiri17y ago
Thanks for your suggestion.

Well In my C# application, I have created the following structure and used Marshal.PtrToStructure.
[StructLayout(LayoutKind.Sequential)]
public class Component
{
    public string Name;
    public string Id;
    public string Version;
    public string Description;
    [MarshalAs(UnmanagedType.Struct)]
    public Component Parent;
    [MarshalAs(UnmanagedType.ByValArray)]
    public List Children;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////
int intptr = LoadLibrary("SampleModuleDLL.dll");
IntPtr procAd = (IntPtr)GetProcAddress(intptr, "TestEnumerate");
TestDelegate testStartfunc = (TestDelegate)Marshal.GetDelegateForFunctionPointer(procAd, typeof(TestDelegate));
IntPtr pointerToFunc = testStartfunc();
component = (Component)Marshal.PtrToStructure(pointerToFunc, typeof(Component));

When I run my application, Marshal.PtrToStructure is throwing an exception..

Cannot marshal field 'Parent' of type 'ConsoleApplication2.Component': There is no marshaling support for this type.
System.TypeLoadException: Cannot marshal field 'Parent' of type 'ConsoleApplication2.Component': There is no marshaling support for this type.
   at System.Runtime.InteropServices.Marshal.PtrToStructureHelper(IntPtr ptr, Object structure, Boolean allowValueClasses)
   at System.Runtime.InteropServices.Marshal.PtrToStructure(IntPtr ptr, Type structureType)

Could you please tell me where is the error?
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