How to Persist Dynamic user control data

 
  How to persist dynamically created user control data , here user control is changing in the selected index changed event . how to store the   data of controls in user control like textbox  dropdown etc.. , 

  Actually what i have done is i wrote the below logic in user control page_load event  like this    
 txtNumber.Text      = Request.Form[txtNumber.UniqueID]

 from this line i can get the previous values .
 
 is this a  better approach ? 
  Is there any other approach to persist user control data which contains more controls in it ? 

Thanks in advance .