c# - Javascript values not updating after dropdown selection -

i have value i'm passing server side c# code client side javascript need update based on dropdown selection. value gets changed required in c# logic value change never picked client.

here c# code setting value

protected void ddlcurrency_onselectedindexchanged(object sender, eventargs e) {     dropdownlist ddlcurrencytype = (dropdownlist)upfilter.findcontrol("ddlcurrency");      currencyid = int.parse(ddlcurrencytype.selecteditem.value); }  private void setcurrencysymbol() {     if (currencyid == 2)     {         currencysymbol = "€";     }     else     {         currencysymbol = "$";     }  } 

and javascript variable

var currencysymbol = "<%=currencysymbol%>"; 

the setcurrencysymbol method called in if(!page.ispostback) condition.

here dropdownlist code

<asp:dropdownlist runat="server" id="ddlcurrency" onselectedindexchanged="ddlcurrency_onselectedindexchanged" autopostback="true" onchange="setcurrencysymbol"> </asp:dropdownlist> 

that javascript variable needs set c# value after new item selected dropdown. original value when page loaded retained after new selection made however. appreciated. in advance.