C / C++ / MFC

IA* pIA;
CComPtr<IUnknown> pIUnknown;
pIUnknown.CoCreateInstance(__uuidof(A));
pIUnknown->QueryInterface(__uuidof(IA), (LPVOID*)&pIA);

__checkReturn HRESULT CoCreateInstance(__in REFCLSID rclsid, __in_opt LPUNKNOWN pUnkOuter = NULL, __in DWORD dwClsContext = CLSCTX_ALL) throw()
{
    ATLASSERT(p == NULL);
    return ::CoCreateInstance(rclsid, pUnkOuter, dwClsContext, __uuidof(T), (void**)&p);
}

<br />
#include <windows.h><br />
<br />
//Global Definitions<br />
#define WINDOW_WIDTH 980<br />
#define WINDOW_HEIGHT 750<br />
<br />
//Global Variables <br />
const char lpClassName[] = "MyProject";<br />
HWND mainWindow<br />
<br />
//Function Declarations<br />
LRESULT CALLBACK WindowEvent(HWND, UINT message, WPARAM wParam, LPARAM, lParam);<br />
<br />
int WINAPI WinMain(HINSTANCE, hInstance, HINSTANCE, hPrevInstance, LPSTR lpCmdLine, int nShowCmd<br />
<br />
{<br />
	//Create The Windows Class<br />
	WNDCLASSEX wc;<br />
	wc.style = CS_VREDRAW | CS_HREDRAW;<br />
	wc.lpszMenuName = NULL;<br />
	wc.lpfnWndProc = WindowEvent;<br />
	wc.hInstance = hInstance;<br />
	wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);<br />
	wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);<br />
	wc.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);<br />
	wc.cbWndExtra = 0;<br />
	wc.cbSize = sizeof(wc);<br />
	wc.cbClsExtra = 0;<br />
<br />
	//Register the Window Class<br />
	RegisterClassEx(&wc);<br />
<br />
	//Create The Window<br />
	mainWindow = CreateWindowEx(<br />
		NULL,<br />
		lpClassName,<br />
		"MyProject",<br />
		WS_OVERLAPPEDWINDOW | WS_VISIBLE, <br />
		(GetSystemMetrics(SM_CXSCREEN) / 2 - (WINDOW_WIDTH / 2),<br />
		(GetSystemMetrics(SM_CYSCREEN) / 2 - (WINDOW_HEIGHT / 2),<br />
		WINDOW_WIDTH,<br />
		WINDOW_HEIGHT<br />
		NULL,<br />
		NULL,<br />
		hInstance,<br />
		NULL<br />
		);<br />
<br />
	//Make Sure The Window Was A Sucess<br />
	if (!mainWindow)<br />
		return 0;<br />
	<br />
	//Update The Window<br />
	UpdateWindow(mainWindow);<br />
<br />
	//The Main Loop<br />
	MSG msg;<br />
	while (1)<br />
	{<br />
		if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))<br />
		{<br />
			if (msg.message == WM_QUIT)<br />
			{<br />
			TranslateMessage(&msg);<br />
			DispatchMessage(&msg);<br />
	}<br />
<br />
	return (int) msg.wParam;<br />
	}<br />
	<br />
//Callback Function (WindowEvent)<br />
LRESULT CALLBACK WindowEvent(HWND, UINT message, WPARAM wParam, LPARAM, lParam);<br />
{<br />
	switch (message)<br />
	{<br />
	case WM_DESTROY:<br />
		PostQuitMessage(0);<br />
		return 0;<br />
		break;<br />
	}<br />
<br />
	return DefWindowProc(hWnd, message, wParam, lParam);<br />
}<br />

HBRUSH CTestDlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
   // Call the base class implementation first! Otherwise, it may
   // undo what we're trying to accomplish here.
   HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);

   // Are we painting the IDC_MYSTATIC control? We can use
   // CWnd::GetDlgCtrlID() to perform the most efficient test.
   if (pWnd->GetDlgCtrlID() == IDC_MYSTATIC)
   {
      // Set the text color to red
      pDC->SetTextColor(RGB(255, 0, 0));

      // Set the background mode for text to transparent 
      // so background will show thru.
      pDC->SetBkMode(TRANSPARENT);

      // Return handle to our CBrush object
      hbr = m_brush;
   }
   return hbr;
}

BOOL CTestDlg::OnEraseBkgnd(CDC* pDC)
{
      // Set brush to desired background color
      CBrush backBrush(RGB(255, 128, 128));

      // Save old brush
      CBrush* pOldBrush = pDC->SelectObject(&backBrush);

      CRect rect;
      pDC->GetClipBox(&rect);     // Erase the area needed

      pDC->PatBlt(rect.left, rect.top, rect.Width(), rect.Height(),
          PATCOPY);
      pDC->SelectObject(pOldBrush);
      return TRUE;
}