Dropdownlist onselectedindexchanged问题

Question

I have a dropdownlist like this

<asp:dropdownlist runat="server" autopostback="true" onselecteditemindexchanged="fire_event" ID="DDL"/>

and on codebehind im doing this

page_load : if(!page.postback)I m binding data into dropdownlist
   fire_event: I am redirecting page to itemselected value.

So I am able to do most of the part everything is working perfectly except..

when i select item in dropdown it redirects me to the page I wanted..but when i click back it remains at the same item selected value .I want it to be like that it loads again when i click back for eg

if my dropdown is like state A and other items

A
B
C
D

when I select D it takes me to page D and when i click back it is at state D i want it to show A instead of D

Answer 1

When you use the back button on many(though not necessarily all) browsers you are not hitting the server, you are retrieving a copy of the page that has been cached by the browser in it's last state.
To avoid this you will need to prevent your page from being cached so that it is retrieved from the server instead. Adding the following to your page load will certainly do the trick in IE. Further investigation has revealed that this can also be achieved in Firefox using the no-store attribute:

    Response.CacheControl = "no-cache";
    Response.Cache.SetNoStore();
    Response.AddHeader("Pragma", "no-cache");
    Response.Expires = -1;

Answer 2

You can use javascript to ensure that the right value is selected when the document is loaded. The following code is with jquery but you can do the same with Microsoft Ajax...

$.ready(function() {
    $("#mySelect").val(''); // Set the default value to select here
});

Have a good day!