Makes the dialog visible and brings it to the front
of the display.
@return a string describing the absolute path of the first selected file,
or null if the dialog was cancelled or an error occurred
@exception SWTException <ul>
<li>ERROR_WIDGET_DISPOSED - if the dialog has been disposed</li>
<li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the dialog</li>
</ul>
Makes the dialog visible and brings it to the front of the display.
@return a string describing the absolute path of the first selected file, or null if the dialog was cancelled or an error occurred
@exception SWTException <ul> <li>ERROR_WIDGET_DISPOSED - if the dialog has been disposed</li> <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the dialog</li> </ul>