c# - get the value of dropdown on asp button click -

i'm trying populate on dropdown(i.e dropdown2) on value basis of other dropdown(i.e dropdown1), it's populate fine,now problem when i'm click on asp button selected value of dropdown 2 return blank value, i'm not not understand going wrong?

html

<select runat="server" id="ddlfilter" clientidmode="static">     <option value="0">both</option>     <option value="1">add new</option>     <select runat="server" id="ddldepartment" clientidmode="static"></select>     <asp:button id="btnsearch" runat="server" text="show report" cssclass="search_btn" onclick="btnsearch_click" /> 

js

<script> $(document).ready(function () {     $("#ddlfilter").change(function () {         if ($("#ddlfilter").val() > 0) {             $("#ddldepartment").append( < option > new < option > );         }     }); }); </script> 

c#

protected void btnsearch_click(object sender, eventargs e) {     string val= ddldepartment.value; } 

you can't selected value dropdown if adding options in javascript. can use:

string selectedvalue = request.form[ddldepartment.uniqueid]; 

see question