Using wp_dropdown_categories in widget options

I got it 🙂 thanks to this

function update( $new_instance, $old_instance ) {
        $instance = $old_instance;

        //Strip tags from title and name to remove HTML 
        $instance['title'] = strip_tags( $new_instance['title'] );
        $instance['kwtax'] = strip_tags( $new_instance['kwtax'] );

        return $instance;
    }

    function form( $instance ) {

        //Set up some default widget settings.
        $defaults = array( 'title' => __('Equipment Search', 'agriquip'), 'kwtax' => '');
        $instance = wp_parse_args( (array) $instance, $defaults );
        ?>
        <p>
            <label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e('Title:', 'agriquip'); ?></label>
            <input id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" value="<?php echo $instance['title']; ?>" class="widefat" />
        </p>

          <p>
            <select id="<?php echo $this->get_field_id('kwtax'); ?>" name="<?php echo $this->get_field_name('kwtax'); ?>" class="widefat" style="width:100%;">
                <?php foreach(get_terms('exc_equipment_cat','parent=0&hide_empty=0') as $term) { ?>
                <option <?php selected( $instance['kwtax'], $term->term_id ); ?> value="<?php echo $term->term_id; ?>"><?php echo $term->name; ?></option>
                <?php } ?>      
            </select>
        </p>