* dialog and adds the selected configuration.
*/
private void handleAddButtonPressed() {
ElementTreeSelectionDialog dialog = new ElementTreeSelectionDialog(
SpringUIUtils.getStandardDisplay().getActiveShell(),
new WorkbenchLabelProvider(), new WorkbenchContentProvider());
dialog.setTitle(Activator.getResourceString(DIALOG_TITLE));
dialog.setMessage(Activator.getResourceString(DIALOG_MESSAGE));
dialog.addFilter(new ConfigFileFilter(new String[] { "xml" }));
dialog.setValidator(new FileSelectionValidator(true));
dialog.setInput(element);