protected function beforeValidate()
 {
     $model = $this->getFields();
     foreach ($model as $field) {
         if ($field->field_type == "LIST") {
             $fname = $field->varname;
             if ($this->{$fname} && is_array($this->{$fname})) {
                 $this->{$fname} = implode(",", $this->{$fname});
             }
         }
     }
     return parent::beforeValidate();
 }