How to make an Update in a retrieve plugin

Hi guys

I need to change the value of a checkbox to trigger a workflow in crm 2013

the plugin is in retrieve and it's post operation
and the workflow starts its execution when that checkbox change its value

In fact the code itself didn't update the true or false value of the checkbox


Can you help me to make me see my error or see what I'm missing

Thanks in advance

this is my code

if (requestEntity.pwc_HasRequestItemsandInquiryType == false)
    {
       requestEntity.pwc_HasRequestItemsandInquiryType = true;
                        
                       
     }
else if (requestEntity.pwc_HasRequestItemsandInquiryType == true)
     {
        requestEntity.pwc_HasRequestItemsandInquiryType = false;
                       
      }