how to maintain radio button list in grid view paging

As you are using gridview paging, it does postback when you goes to next page. So previous state of radio will removed from browser memory. Inorder to resolve problem, you need to use ViewState or cookie or LocalStorage(client side). Please look below links:

 

https://www.aspsnippets.com/Articles/Preserving-state-of-Checkboxes-while-paging-in-ASP.Net-GridView-Control.aspx

 

https://code.msdn.microsoft.com/Maintance-the-CheckBox-7b9e9e1e 

 

http://highoncoding.com/Articles/697_Persisting_CheckBox_State_While_Paging_in_GridView_Control.aspx