这里给出的方法是在 WM_INITDIALOG 事件里实现居中处理。
下面是对话框窗口过程

BOOL CALLBACK MainDialogProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{switch (uMsg){case WM_INITDIALOG: {		HWND hwndOwner = NULL;RECT rcOwner, rcDlg, rc;			// Get the owner window and dialog box rectangles. 			if ((hwndOwner = GetParent(hDlg)) == NULL) {hwndOwner = GetDesktopWindow(); }			GetWindowRect(hwndOwner, &rcOwner); GetWindowRect(hDlg, &rcDlg); CopyRect(&rc, &rcOwner); // Offset the owner and dialog box rectangles so that right and bottom // values represent the width and height, and then offset the owner again // to discard space taken up by the dialog box. OffsetRect(&rcDlg, -rcDlg.left, -rcDlg.top); OffsetRect(&rc, -rc.left, -rc.top); OffsetRect(&rc, -rcDlg.right, -rcDlg.bottom); // The new position is the sum of half the remaining space and the owner's // original position. SetWindowPos(hDlg, HWND_TOP, rcOwner.left + (rc.right / 2), rcOwner.top + (rc.bottom / 2), 0, 0,          // Ignores size arguments. SWP_NOSIZE); if (GetDlgCtrlID((HWND) wParam) != IDD_DIALOG_MAIN) { SetFocus(GetDlgItem(hDlg, IDD_DIALOG_MAIN));return FALSE; } return TRUE;}case WM_CLOSE:{EndDialog(hDlg, 0);return TRUE;}}return FALSE;
}