<script type="text/javascript">
function
isNumberKey(evt) {
var charCode =
(evt.which) ? evt.which : event.keyCode;
if
(charCode
>= 48 && charCode <= 57) {
return
true;
}
else {
alert('number
only');
return
false;
}
}
</script>
<asp:TextBox ID="TextBox2"
runat="server"
onkeypress="return isNumberKey(event)"
></asp:TextBox>