protected function renderFilterCellContent()
 {
     if (is_string($this->filter)) {
         echo $this->filter;
     } elseif ($this->filter !== false && $this->grid->filter !== null && $this->name !== null && strpos($this->name, '.') === false) {
         if (is_array($this->filter)) {
             echo CHtml::activeDropDownList($this->grid->filter, $this->name, $this->filter, array('id' => false, 'prompt' => '', 'class' => 'form-control'));
         } elseif ($this->filter === null) {
             echo CHtml::activeTextField($this->grid->filter, $this->name, array('id' => false, 'class' => 'form-control'));
         }
     } else {
         parent::renderFilterCellContent();
     }
 }