<asp:RadioButtonList ID="rbl" runat="server" AutoPostBack="false" RepeatLayout="Table" OnSelectedIndexChanged="rbl_SelectedIndexChanged">
    <asp:ListItem Value="1">A選項</asp:ListItem>
    <asp:ListItem Value="2">B選項</asp:ListItem>
    <asp:ListItem Value="3">C選項</asp:ListItem>
</asp:RadioButtonList>

public int sel;
protected void rbl_SelectedIndexChanged(object sender, EventArgs e)
{
        sel = Convert.ToInt32(rbl.SelectedItem.Value);
        swith(sel)
        {
              case 1:
                      Response.Redirect("A.aspx");
                      break;
              case 2:
                      Response.Redirect("B.aspx");
                      break;
              case 3:
                      Response.Redirect("C.aspx");
                      break;
              default:
                      break;
        }
}