Using VS2005, VB code behind and javascript. 

I have several pages that when accessed for a second or subsequent times always need to hit the server - but what I'm seeing with some users is that they are accessing cached pages. I want to force these pages to always get the latest page from the server.

From client side javascript I know how to set the "if-modifed-since" request header to ensure that my xmlHttpRequest's are always served, i.e. "xmlHttp.setRequestHeader("If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT");". When I view the request headers collection from this request I see "If-Modified-Since" with a value of "Sat, 1 Jan 2000 00:00:00 GMT" in the list.

My problem is that I want my aspx page requests - not just ones that originate from javascript - to have the "If-Modified-Since" request header set to an old date. Stated another way, I want all my pages to come back with the "If-Modified-Since" value in the Header's collection  set to some date (i.e. "Sat, 1 Jan 2000 00:00:00 GMT") that will ensure that the page gets served from the server vs. cache.

Having javascript requests under control, I now need to do the same for all my aspx pages. Here is what I have tried in my code behind. 

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        Response.AddHeader("Last-Modified", "Sat, 1 Jan 2000 00:00:00 GMT")

        Response.AddHeader("If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT")

    End Sub

Good afternoon celoftis, try adding the following in your pageload() event:

Response.AppendHeader("Cache-Control", "no-store");

You can use meta tags.

<META HTTP-EQUIV="Pragma" CONTENT="no-cache">

What I did was change all my aspx pages to extend from a common class (BasePage). Then in the OnLoadComplete event in the BasePage, I added all kinds of Response (see below) - but when I access these pages then check my trace.axd for the Request, I don't see anything in the Headers collection or the server variables (ALL_HTTP, ALL_RAW, etc.) that leads me to believe that the page isn't expired in cache. How can I verify that the page isn't being cached but downloaded each time?

"BasePage" code below:

Public Class BasePage

    Inherits System.Web.UI.Page

    Protected Overrides Sub OnLoadComplete(ByVal e As System.EventArgs)

        If Page.IsPostBack Then

        Else

            Response.AppendHeader("Pragma", "no-cache")

            Response.AppendHeader("Cache-Control", "no-store");  

            Response.Cache.SetNoStore()

            Response.Cache.SetExpires(DateTime.Parse(DateTime.Now.ToString()))

            Response.Cache.SetCacheability(HttpCacheability.NoCache)

            Response.Expires = -1

        End If

        MyBase.OnLoadComplete(e)

    End Sub

End Class

I believe the code above worked. To verify I downloaded Fiddler2 and watched all the requests and responses come back with code 200 or 302. Thanks for the suggestions.