
<script  runat="server">
sub submit(sender As Object, e As EventArgs)
if Page.IsValid then
   lbl.Text=""
else
   lbl.Text=""
end if
end sub
</script>

<html>
<body>

<form runat="server">
请输入 US 
<asp:TextBox id="txtbox1" runat="server" />
<br /><br />
<asp:Button text="提交" OnClick="submit" runat="server" />
<br /><br />
<asp:Label id="lbl" runat="server" />
<br />
<asp:RegularExpressionValidator
ControlToValidate="txtbox1"
ValidationExpression="\d{5}"
EnableClientScript="false"
ErrorMessage=""
runat="server" />
</form>

</body>
</html>