<!DOCTYPE html>
<html>
<body>
   <form runat="server">
     <p>ValidationGroup 1</p>
      <p>You must select one item in the list (Test with no items selected to get error)</p>
      <p>Age:</p>
      <asp:RadioButtonList id="rb1" ValidationGroup="valGroup1" runat="server">
           <asp:ListItem Value="Over 21" />
           <asp:ListItem Value="Under 21" />
      </asp:RadioButtonList>

      <asp:RequiredFieldValidator id="ReqField1"
      ControlToValidate="rb1" ValidationGroup="ValGroup1"
      ErrorMessage="Required" runat="server" />
      <asp:Button id="Bt1" Text="Validate" runat="server"
      CausesValidation="True" ValidationGroup="ValGroup1" />

      <p>ValidationGroup 2</p>
      <p>You must select one item in the list (Test with no items selected to get error)</p>
      <p>Gender:</p>
      <asp:RadioButtonList id="rb2" ValidationGroup="valGroup2" runat="server">
           <asp:ListItem Value="Male" />
           <asp:ListItem Value="Female" />
      </asp:RadioButtonList>

      <asp:RequiredFieldValidator id="ReqField2"
      ControlToValidate="rb2" ValidationGroup="ValGroup2"
      ErrorMessage="Required" runat="server" />
      <asp:Button id="Bt2" Text="Validate" runat="server"
      CausesValidation="True" ValidationGroup="ValGroup2" />
   </form>
</body>
</html>