只需修改OnPaint方法

LONG OnPaint(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)

{

PAINTSTRUCT ps;

HDC hdc;

RECT rect;

HPEN hpen;

GetClientRect(hWnd,rect);

hdc = BeginPaint(hWnd,ps);

//hpen = GetStockPen(BLACK_PEN); //兩種創建畫筆的方法

hpen = CreatePen(PS_SOLID,2,RGB(0XFF,0X00,0X00));

HGDIOBJ oldpen = SelectObject(hdc,hpen);

Ellipse(hdc,10,10,200,200);

SelectObject(hdc,oldpen);

DeleteObject(hpen);

EndPaint(hWnd,ps);

return TRUE;

}