ASP Validation avoid postback

 If you like to validate your fields on click of radiobutton or Checkboxes you need to manually add "CausesValidation="true" as by default it is disabled.

<asp:RadioButtonList ID="rblNineteen1" CausesValidation="true" runat="server" AutoPostBack="true" OnSelectedIndexChanged="rblNineteen1_SelectedIndexChanged" RepeatDirection="Horizontal">