You can do it by jQuery or by code too. Refer the below how to make it by jQuery.
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script type="text/javascript" src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.6.1.min.js"></script>
<script type="text/javascript">
$(function () {
var firstlength = 30;
var secondlength = 100;
BindDropDown("[id*=ddlFirst]", firstlength);
BindDropDown("[id*=ddlSecond]", secondlength);
});
function BindDropDown(dropdown, count) {
// To add default first Item if required
$(dropdown).html(' ');
$("<option></option>")
.attr("value", "")
.text("Please Select")
.appendTo(dropdown);
// Loop Till your count you nedd to add
for (var i = 1; i <= count; i++) {
$("<option></option>")
.attr("value", i)
.text(i)
.appendTo(dropdown);
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
First Drop Down
<select name="DynamicTextDropdown" id="ddlFirst">
</select>
Second Drop Down
<select name="DynamicTextDropdown" id="ddlSecond">
</select>
</div>
</form>
</body>
</html>
Demo
