Managed C++/CLI

// CitectAPIManagedDll.h<br />
<br />
#pragma once<br />
<br />
using namespace System;<br />
using namespace System::Runtime::InteropServices;<br />
<br />
namespace CitectAPIManagedDll<br />
{<br />
	/// Create a unmanaged wrapper structure as the placeholder for unmanaged class <br />
	/// members as exported by the DLL. This structure/class is not intended to be<br />
	/// instantiated by .NET applications directly.<br />
	public __gc struct CitectAPIUnman<br />
	{<br />
		/// Define the virtual table for the wrapper<br />
		typedef __gc struct __VTB<br />
		{<br />
			void (*Open)(CitectAPIUnman*, System::String*, System::String*, System::String*, System::Int32*);	<br />
		};<br />
<br />
	public:<br />
		char* id;<br />
		static __VTB *vtb;	<br />
<br />
		/// Perform all required imports. Use "ThisCall" calling convention to import <br />
		/// functions as class methods of this object (not "StdCall"). Note that we <br />
		/// pass this pointer to the imports. Use the "decorated name" instead of <br />
		/// retreived from the DLL as the entry point.<br />
		[DllImport("CTAPI.dll", <br />
				  EntryPoint="ctOpen", <br />
				  CallingConvention=CallingConvention::ThisCall)]<br />
		static void Open(CitectAPIUnman*, System::String*, System::String*, System::String*, System::Int32*);<br />
		<br />
		/// Delegates of imported virtual methods for the virtual table.<br />
		/// This basically is hacking the limitation of function pointer (FP),<br />
		/// as FP requires function address at compile time.<br />
		static void VOpen(CitectAPIUnman* w, System::String* computer, System::String* username, System::String* password, System::Int32* mode)<br />
		{<br />
			Open(w, computer, username, password, mode);<br />
		}<br />
	};<br />
<br />
	/// Managed wrapper class which will actually be used by .NET applications.<br />
	public __gc class CitectAPIWrap<br />
	{<br />
	public: <br />
		/// User-defined managed wrapper constructor. It will perform a few tasks:<br />
		/// 1) Allocating memory for the unmanaged data<br />
		/// 2) Assign the v-table<br />
		/// 3) Marshall the parameters to and call the imported unmanaged class constructor<br />
		CitectAPIWrap()<br />
		{<br />
			tv = new CitectAPIUnman();<br />
			CitectAPIUnman::vtb->Open = CitectAPIUnman::VOpen;<br />
		}	<br />
<br />
		/// Let the v-table handle method overriding<br />
		virtual void Open(System::String* computer, System::String* username, System::String* password, System::Int32* mode)<br />
		{<br />
			CitectAPIUnman::vtb->Open(tv, computer, username, password, mode);<br />
		}<br />
<br />
	private:<br />
		CitectAPIUnman *tv;<br />
	};<br />
}<br />

	LPCTSTR lpFilename = static_cast<LPCTSTR>(Marshal::StringToHGlobalAnsi(filename).ToPointer());

// Do stuff with lpFilename

	Marshal::FreeHGlobal(static_cast<IntPtr>(const_cast<void*>(static_cast<const void*>(lpFilename))));

const Byte *bp = reinterpret_cast<const Byte*>(filename);

// Find pointer to start of actual char data
if(bp != 0)
{
    unsigned int offset = RuntimeHelpers::OffsetToStringData;
    bp += offset;
}

// Cast to Char pointer
const Char* cFilename = reinterpret_cast<const Char*>(bp);

// Marshal to unmanaged char array
char* bitmapFilename = static_cast<char*>(Marshal::StringToHGlobalAnsi(cFilename).ToPointer());

  // Do stuff with bitmapFilename

Marshal::FreeHGlobal(bitmapFilename);