Yii Set Item per Page CGridView dynamically

In the Controller / ActionAdmin:

 if (isset($_GET['pageSize'])) {  
           Yii::app()->user->setState('pageSize',(int)$_GET['pageSize']);  
           unset($_GET['pageSize']);  
         }  

In the model / Search Function:

 return new CActiveDataProvider(get_class($this), array(  
             'pagination'=>array(  
                 'pageSize'=> Yii::app()->user->getState('pageSize',Yii::app()->params['defaultPageSize']),  
             ),  
             'criteria'=>$criteria,  
         ));  

In the View Admin:

 <?php  
 $pageSize=Yii::app()->user->getState('pageSize',Yii::app()->params['defaultPageSize']);  
 $this->widget('zii.widgets.grid.CGridView', array(  
     'id'=>'file-grid',  
     'dataProvider'=>$model->search(),  
     'columns'=>array(  
         ...,  
         array(  
             'class'=>'CButtonColumn',  
             'header'=>CHtml::dropDownList('pageSize',$pageSize,array(10=>10,20=>20,50=>50,100=>100),array(  
                  'onchange'=>"$.fn.yiiGridView.update('file-grid',{ data:{pageSize: $(this).val() }})",  
           )),  
         ),  
     ),  
 )); ?>  

...'onchange'=>"$.fn.yiiGridView.update('file-grid',{ data:{pageSize:...

change 'file-grid' to your grid view id.

result :