Открытие файла перетаскиванием

    OPENFILENAME ofn;       // common dialog box structure
wchar_t szFile[260];       // buffer for file name
HWND hwnd;              // owner window
HANDLE hf;              // file handle
 
// Initialize OPENFILENAME
ZeroMemory(&ofn, sizeof(OPENFILENAME));
ofn.lStructSize = sizeof(OPENFILENAME);
ofn.hwndOwner = hwnd;
ofn.lpstrFile = szFile;
ofn.nMaxFile = sizeof(szFile);
ofn.lpstrFilter = L"All\0*.*\0Text\0*.TXT\0";
ofn.nFilterIndex = 1;
ofn.lpstrFileTitle = NULL;
ofn.nMaxFileTitle = 0;
ofn.lpstrInitialDir = NULL;
ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
 
// Display the Open dialog box. 
 
if (GetOpenFileName(&ofn)==TRUE) 
    hf = CreateFile(ofn.lpstrFile, GENERIC_READ,
        0, (LPSECURITY_ATTRIBUTES) NULL,
        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL,
        (HANDLE) NULL);

#include <windows.h>
 
static LRESULT CALLBACK wnd_proc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam ) {
    switch ( uMsg ) {
        case WM_DROPFILES: {
            int size = DragQueryFile( (HDROP)wParam, 0, NULL, 0 );
            char * p_filename = new char [size + 1];
            DragQueryFile( (HDROP)wParam, 0, p_filename, size );
            p_filename[size] = '\0';
            MessageBox( NULL, p_filename, "title", MB_OK );
            DragFinish( (HDROP)wParam );
        } break;
 
        case WM_DESTROY:
            PostQuitMessage( 0 );
            break;
 
        default:
            return DefWindowProc( hWnd, uMsg, wParam, lParam );
    }
 
    return 0;
}
 
int main()
{
    HINSTANCE inst = GetModuleHandle( NULL );
 
    WNDCLASS wc;
    ZeroMemory( &wc, sizeof( WNDCLASS ) );
    wc.lpfnWndProc      = wnd_proc;
    wc.hInstance        = inst;
    wc.lpszClassName    = "testcls32";
    wc.hCursor          = LoadCursor( NULL, IDC_ARROW );
    wc.hbrBackground    = (HBRUSH)(COLOR_BTNFACE + 1);
    RegisterClass( &wc );
 
    CreateWindowEx( WS_EX_TOPMOST | WS_EX_ACCEPTFILES, "testcls32", NULL, WS_OVERLAPPEDWINDOW | WS_VISIBLE, 100, 100, 300, 200, NULL, NULL, inst, NULL );
 
    MSG msg;
    while ( GetMessage( &msg, NULL, 0, 0 ) ) {
        TranslateMessage( &msg );
        DispatchMessage( &msg );
    }
 
    return 0;
}