Question about C# wrappers

I have written a few C# programs (VS2010) which call C++ native code DLLs, via DLLImport.

I gather that with OpenCascade I need to provide wrappers and am considering buying the wrapper package from OpenCascade SAS.

But I would like to understand what is involved.

Specifically, looking at the C# sample, the file OCCViewer.CPP appears to consist not of wrappers but of another class altogether (OCCViewer) which calls the OCC library. For instance, this includes the simple function:

void OCCViewer::RedrawView(void)
{
if (!myView.IsNull())
myView->Redraw();
}

Redraw is defined in V3dViewer.hxx as:

Standard_EXPORT void Redraw() const;

V3dViewer.hxx is listed as an external dependency of the OCC project (which produces a C++/CLI DLL).

Standard_Export is defined in Standard_Macro.hxx as:

define Standard_EXPORT __declspec( dllexport )

"DllImport" never appears in this code.

What part if this is considered a "wrapper"?

Is there a discussion somewhere on how to create these wrappers?

I am aware of the difference between statically and dynamically loaded DLLs. DLLImport appears to generate a dynamically loaded reference, while the code above generates a statically loaded one. I can't find anything in my book about C# that addresses how to create a static DLL reference. Can someone point me to such a description?

Thanks in advance,
Michael Bate