Marshalling CodeElements to an IntPtr in C#

Question

I am writing a Visual Studio add in and need to marshall a managed CodeElements object to it's unmananged form. I just need the pointer in memory, as I can cast it and treat it like a CodeElement on the unmanaged side.

    [DllImport("CodeMethodsToString.dll")]
    private static extern BSTR* CodeMethodsToString(void* functionObject);

    public static void CodeMethodsToXML(XmlElement parent, CodeElements elements)
    {
        //Call CodeMethodsToString: how do I marshall CodeElements to an IntPtr?
        //set XmlElement in here
    }

I know how to deal with the XML, and I have a working version of this in C#. I created the unmanaged DLL because calling all of the various member variables at the lowest level of recursion was killing the speed of the program. I simply need to know how to use System.Runtime.Interop.Marshal to convert the CodeElements object to a pointer to the COM object in memory.

Thanks.

Answer 1

Looks like Jonathan was close. This is how I'd do it:

[DllImport("CodeMethodsToString.dll")]
[return: MarshalAs(UnmanagedType.BStr)]
private static extern string CodeMethodsToString(IntPtr functionObject);

public static void CodeMethodsToXML(XmlElement parent, CodeElements elements)
{
   GCHandle pin;
   try
   {
      pin = GcHandle.Alloc(elements, GCHandleType.Pinned);
      string methods = CodeMethodsToString(pin.AddrOfPinnedObject());
    }
    finally
    {
       pin.Free();
    }
}