<!DOCTYPE html>
<html>
<body>
    <form runat="server">
      <p>ValidationGroup 1</p>
      Name:<asp:textbox id="tbName" runat=Server />
      <asp:requiredfieldvalidator id="ReqFieldVal1"
      controltovalidate="tbName"
      validationgroup="valGroup1"
      errormessage="Required" runat=Server />
      <br>
      Age:<asp:textbox id="tbAge" runat=Server />
      <asp:requiredfieldvalidator id="ReqFieldVal2"
      controltovalidate="tbAge"
      validationgroup="valGroup1"
      errormessage="Required" runat=Server />
    
      <br><br>
       <asp:ImageButton id="Button1" ImageUrl="img_submit.jpg"
       causesvalidation=true
      validationgroup="valGroup1" runat=Server />
       <p>ValidationGroup 2</p>
      
       City<asp:textbox id="tbCity" runat=Server />
       <asp:requiredfieldvalidator id="ReqFieldVal3"
       controltovalidate="tbCity"
      validationgroup="valGroup2"
      errormessage="Required" runat=Server />
    
      <br><br>
      <asp:ImageButton id="Button2" ImageUrl="img_submit.jpg"
      causesvalidation=true
      validationgroup="valGroup2" runat=Server />
    </form>
</body>
</html>