ASP.NET

<%@ Page Title="test" Language="C#" MasterPageFile="~/Template.master" CodeFile="Define.aspx.cs" Inherits="JobRecords_Default" EnableEventValidation="false"%>

<script type="text/javascript">
function changeFunc() {
var selectBox = document.getElementById("selectBox");
var selectedValue = selectBox.options[selectBox.selectedIndex].value;
window.location.href = '?s=' + selectedValue;
}
</script>

<form role="form">
<label>Ward:</label>
<select id="selectBox" class="form-control" onchange="changeFunc();" runat="server">
<option value="1">Ward 1</option>
<option value="2">Ward 2</option>
<option value="3">Ward 3</option>
</select>
<asp:Button ID="btnRegister" CssClass="btn btn-lg btn-block btn-success" runat="server" Text="Register" OnClick="btnRegister_Click" ></asp:Button>
</form>

changeFunc()

Quote:

Invalid postback or callback argument. Event validation is enabled using <pages enableeventvalidation="true"> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.