I have created multiple RadioButtonList for user to check, these radobuttonLists are are created dynamically according to the db records, and they are created at Page_load event.
When user clicked save, I want to check if there is any radio lists that is unanswered, I basically go through each controls in the placeholder
foreach (control ctl in Placeholder.controls)
if (clt.SelectedIndex == -1)
---Do something to display error message --
However this code always got error of "Object reference not set to an instance of an object", I already try to recreate all the controls when posted back in Page_Init event, but still not successful.
Appreciate your help.