In order to get dropped files(AKA: file(s) which were dragged onto the window control)
you'll have to accomplish two steps:
Note that the DragQueryFile also retrieves directories!
1.Add the accept-files style to the window control
DWORD dwStyle = GetWindowLong(hWnd, GWL_EXSTYLE);
SetWindowLong(hWnd, GWL_EXSTYLE, dwStyle | WS_EX_ACCEPTFILES);
2.In the window procedure proccess the WM_DROPFILES message
HDROP hDrop = (HDROP)wParam;
DWORD DropsNo = DragQueryFile(hDrop, -1, NULL, 0);
for (DWORD i = 0; i < DropsNo; i++)
DragQueryFile(hDrop, i, tmp, 256);
MessageBox(NULL, tmp, "", MB_OK); // Do anything with the data...