Question

I have seen several posts online complaining that Firefox maintains the history url hash after redirecting.. That is the behavior I am hoping for – and it happens in Firefox (11.0), Chrome (18.0), and Opera (11.61), but not IE (9) or Safari (5.1.2).

On my page, I have ASP.NET 4.0 history points set up and working (has been working for a couple years). I also pass a few querystring params to the page. What I am trying to do now is check the value of a new querystring param, and if it does not match what I am expecting, redirect to the same page with an updated value. I am using this mechanism to track the session of individual tabs of a browser so that when they have the same page open in multiple tabs, the session values dont step on each other from tab to tab.

Anyway, I have everything working correctly including the back/forward using ASP.NET History points – and when I visit a bookmark and the querystring param does not match, I redirect and change the querystring param to track the session, and the history state that is in the url of the bookmark is then used to reload the page to the state I want. But that only works in Firefox, Chrome, and Opera. Not IE which is the big one for me (based solely on our user base), and not Safari.

I have identified that in addition to (or perhaps because of) the fact that the url history state is not present, ScriptManager.Navigate is not called after the redirect in IE or Safari.

Is there a setting/option that I can set on the ScriptManager or during the redirect to maintain the History state in the url? If the history state was in the url, I could call ScriptManager.Navigate directly if I needed to, but the values are not present in the url.

If it helps at all, here’s a listing of where I do the check and redirect. The ReportRunID is then appended to the session variable keys that need to be unique to each tab. I keep a listing of previous ReportRunIDs to keep track and to clean them out (after a certain time period, or when more than [MAX] ids are encountered) so that I dont overload server memory with these session entries.

Private Sub Page_PreInit(sender As Object, e As System.EventArgs) Handles Me.PreInit

    If IsPostBack = False Then
        Dim rrid As String = Request.QueryString("RRID")
        If ReportRunIDExists(rrid) = False Then
            ReportRunID = Now.ToString("_HHmmssfff")
            Dim url As String = Request.Url.PathAndQuery

            If String.IsNullOrEmpty(rrid) Then
                Response.Redirect(String.Format("{0}&RRID={1}", url, _reportRunID))
            Else
                Dim idx As Integer = url.IndexOf("&RRID=")
                Response.Redirect(String.Format("{0}&RRID={1}{2}", url.Substring(0, idx), _reportRunID, url.Substring(idx + 6 + rrid.Length)))
            End If
        End If
    End If

End Sub

Private Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
    'save current RRID/Page/Time to session
    UpdateSessionReportRunID(_reportRunID)
End Sub

…

If my bookmarked url looks like:

mysite.com/mypage.aspx?Rpt=123&RRID=_095224678#&&state1=abc&state2=def...

In FF/Chrome/Opera after the redirect, my url looks like:

mysite.com/mypage.aspx?Rpt=123&RRID=_102176253#&&state1=abc&state2=def...

But in IE/Safari after redirect, my url looks like:

mysite.com/mypage.aspx?Rpt=123&RRID=_102176253

Any ideas?

Answer 1

After much more searching, I have come to the realization that History State hash is not sent to the server. It is stored in the querystring so that it is included in bookmarks, but it is accessed by the client-side scriptmanager which causes a postback to load the state values. Since the Server never sees the hash value in the querystring, I have no way of finding those values when a user follows a bookmark to that page.

This problem was introduced as I was trying to start tracking the session state of different browser tabs individually. In my code above, if the RRID parameter is empty or invalid, I have to redirect to self with a new RRID value. When I do that redirect the History State hash was being lost for IE and Safari (but not for the other browsers).

My workaround:

The problem is that I needed to include the hash value in my redirect, but that is not available from the server, so I decided to inject some javascript to the page to perform the redirect from the client where the hash is available.

I already had a Client Redirect extension helper method that I have used in different scenarios, and I modified it to include the current hash value:

<System.Runtime.CompilerServices.Extension()>
Public Sub ClientRedirect(ByVal Response As HttpResponse, ByVal url As String, Optional ByVal target As Target = Nothing, Optional ByVal windowFeatures As String = Nothing, Optional includeCurrentHash As Boolean = False)

    If IsNothing(target) Then
        If windowFeatures = String.Empty Then
            target = ResponseHelper.Target._self
        Else
            target = ResponseHelper.Target._blank
        End If
    End If

    Dim page As Page = CType(HttpContext.Current.Handler, Page)
    url = page.ResolveClientUrl(url)

    Dim script As String
    script = "window.open(""{0}"", ""{1}"", ""{2}"");"

    script = String.Format(script, url & If(includeCurrentHash, "#"" + window.location.hash + """, String.Empty), target.ToString, windowFeatures)
    If target = ResponseHelper.Target._self Then
        'execute after page has loaded
        page.ClientScript.RegisterStartupScript(GetType(Page), "Redirect_" & Now.ToString("HHmmssfff"), script, True)
    Else
        'execute as page is loading
        page.ClientScript.RegisterClientScriptBlock(GetType(Page), "Redirect_" & Now.ToString("HHmmssfff"), script, True)
    End If

End Sub

Then in my Page_PreInit where I do the redirects, I changed that to do the ClientRedirect including the current hash, and that has gotten the desired result:
Redirecting the browser while maintaining the History State hash on all browsers.

    'redirect from the client so that we keep the History State URL hash 
    Response.ClientRedirect(String.Format("{0}&RRID={1}", Request.Url.PathAndQuery, _reportRunID), , , True)