A simple Firefox Addon with XP-COM Component

//in this file you got to write the implementation code
#include "stdafx.h"
#include "CodeprojectXPCOMImpl.h"

#include <nsStringApi.h>
#include <WINUSER.h>
#include <ShellApi.h>
#pragma comment( lib, "shell32.lib")

////////////////////////////////////////////////
//the implementation which will do the work
NS_IMPL_ISUPPORTS1(CCodeprojectXPCOM, ICodeprojectXPCOM)

CCodeprojectXPCOM::CCodeprojectXPCOM()
{
	wcscpy( m_szHomepage, TEXT("www.codeproject.com") );
}

CCodeprojectXPCOM::~CCodeprojectXPCOM()
{
}
NS_IMETHODIMP CCodeprojectXPCOM::Action(int cmd,const nsAString &nsString, int *_retval)
{
	*_retval = 0;//everything is fine
	switch( cmd )
	{
	case 0:
		MessageBox( 0, TEXT("Running operation 0"), TEXT("XP-COM"), MB_OK );
		break;
	case 1:
		{
			const PRUnichar* data = 0;
			PRUint32 len = NS_StringGetData(nsString, &data);

			TCHAR szBuffer[200];
			memset( szBuffer, 0, sizeof(szBuffer) /sizeof(TCHAR) );
			wcsncpy( szBuffer, data, len );

			HINSTANCE result = ::ShellExecute( NULL, TEXT( "explore" ), szBuffer, NULL,NULL, SW_SHOW );
		}
		break;
	}
	return NS_OK;
}
NS_IMETHODIMP CCodeprojectXPCOM::GetAboutText(class nsAString &nsString)
{
	TCHAR szBuffer[200];
	wcscpy( szBuffer, TEXT("XP-COM dll from Codeproject") );
	nsString.Assign( szBuffer );

	return NS_OK;
}
NS_IMETHODIMP CCodeprojectXPCOM::GetHomepage(class nsAString &nsString)
{
	nsString.Assign( m_szHomepage );
	return NS_OK;
}
NS_IMETHODIMP CCodeprojectXPCOM::SetHomepage(class nsAString const &nsString)
{
	const PRUnichar* data = 0;
    PRUint32 len = NS_StringGetData(nsString, &data);

	memset( m_szHomepage, 0, sizeof(m_szHomepage) /sizeof(TCHAR) );
	wcsncpy( m_szHomepage, data, len );

	TCHAR szBuffer[400];
	_swprintf( szBuffer, TEXT("The new homepage is '%s' now."), m_szHomepage );

	MessageBox( 0, szBuffer, TEXT("XP-COM"), MB_OK );

	return NS_OK;
}