javascript - Calling code behind with event handler not working -

i have web page consists of 2 dropdown boxes , gridview. have created web service collects data drop down boxes , have used ajax call populate them. issue having when try add onselectedindexchanged event handler, not seem working correctly. have looked around , have tried few things. have set enableeventvalidation false (i presume fixed issue related ddl being populated dynamically in js). have enabled autopostback on ddl.

when change ddl index, page seems posting dll index reverses previous selected index.

<div class="row control-group">      <div class="form-group col-xs-12" id="mailbox">            <label>which bills view?</label>            <asp:dropdownlist id="ddldepartment" runat="server" cssclass="form-control"></asp:dropdownlist>            <asp:dropdownlist id="ddluser" runat="server" cssclass="form-control" onselectedindexchanged="ddluser_selectedindexchanged" autopostback="true"></asp:dropdownlist>            <p class="help-block text-danger"></p>     </div> </div> 

the var = 1; can put breakpoint there.

protected void ddluser_selectedindexchanged(object sender, eventargs e) {    var = 1; } 

below ajax request , generating of grid

function getusers() {    var department = $('select#maincontent_ddldepartment option:selected').val();    $.ajax({       type: "get",       url: "webserviceurl" + department + "",       contenttype: "json",       datatype: "json",       async: false,       success: function (data) {           var ddlusers = $("#maincontent_ddluser");           ddlusers.empty();           $.each(data, function () {               ddlusers.append($("<option></option>").val(this['samaccountname']).html(this['displayname']));           });       },       error: function (xhr) {       }   }) } 

thanks

you can't this.there security feature built asp.net called event validation prevents posting data not there when page created server.

you (or hacker) changing drop down options using javascript , tries submit changes server through selectedindexchanged - can see why not allowed?

as workaround can implement achange() event on drop down using jquery , make server side call using $.ajax:

$("#ddluser").change(function () {     alert("write $.ajax call call server here..."); });