<script  runat="server">
   Sub SubmitBtn(obj As Object, e As EventArgs)
     lblMsg.Text = "Submitted using the ASP.NET postback mechanism."
   End Sub
   </script>

<!DOCTYPE html>
<html>
<body>
   <form runat="server">
      Click the button:
   <asp:button id="Button1" Text="Submit" onclick="SubmitBtn"
      UseSubmitBehavior="FALSE" runat="server"/>
     <br>
     <asp:label id="lblMsg" runat="server"/>
   </form>
</body>
</html>