Browser back button loads old page with old javascript

Question

Page 1 has the flowing code logic when pressing a button

If MyDataIsValid() Then
    ScriptManager.RegisterStartupScript(me, me.GetType(), "PopUp", "", False)
    Response.Redirect("~/Page2", false)
Else
    ScriptManager.RegisterStartupScript(me, me.GetType(), "PopUp", <some js for a popup>, False)
End If

If the fist time I press the button and the data is not valid then then popup will show. The second time I use valid data and the page redirects to Page2. If I navigate backwards by pressing the back button on the browser, the popup will show. That's the problem, the popup will falsely tell me my data is not correct.

I know I can make a button on Page2 to redirect me to Page1 but I also want the back button of the browser to work correctly.

When navigating backwards using the browser back button the Load event in Page1 does not run. The page loads the cached page of the first time I press the button.

I tried

Response.Cache.SetCacheability(HttpCacheability.NoCache)

or the

Response.Buffer = true
Response.CacheControl = "no-cache"
Response.AddHeader("Pragma", "no-cache")
Response.Expires = -1441

so the page will no cache but it dos not work. The page does not reload at back button from the browser.

it doesn't have anything to do with caching, by registering the startup script and performing a postback you're rendering an inline (injected) script into the page. edit: the back button does pull a cached page, but it isn't an client request and server response scenario. — Brett Caswell
you should probably introduce conditional checks into this popup script that suppresses it for this back button scenario. something like a check to ensure the control view state are the same. can you provide a sample of <some js for a popup> and the form. Also, please add the appropriate application tag.. I'm getting the impression this is a webform, is that right? — Brett Caswell
@Brett Caswell: "the back button does pull a cached page", yes, but it's the page from first time I press the button, not the second time, when the data is valid. — mvaculisteanu
the distinction here is that you aren't getting a cache as it relates to a request. the back button is essentially loading a downloaded page from the previous\last response. A response that has an inline script that executes without condition. — Brett Caswell
@BrettCaswell , Correct. Problem is how do I remove the inline script. If I reset the inline script before redirecting it does not work. — mvaculisteanu

G3nt_M3caj G3nt_M3caj · Accepted Answer · 2020-03-25T10:24:16

This is your solution: Setting your script to Blank/Nothing before you redirect routes to another page.

Private Sub WebForm1_PreLoad(sender As Object, e As EventArgs) Handles Me.PreLoad
    If Session.Item("Script") IsNot Nothing Then
        ScriptManager.RegisterStartupScript(Me, Me.GetType(), "PopUp", "<script type='text/javascript'>" & CStr(Session.Item("Script")) & "</script>", False)
    End If
End Sub


Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    If MyDataIsValid() Then
        Session.Item("Script") = ""
        Response.Redirect("~/Page2.aspx")
    Else
        Session.Item("Script") = "alert('Script is running')"
        ScriptManager.RegisterStartupScript(Me, Me.GetType(), "PopUp", "<script type='text/javascript'>" & CStr(Session.Item("Script")) & "</script>", False)
    End If
End Sub

To avoid cached pages by browser work on it history by Javascript (client side) as follows.

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    If MyDataIsValid() Then

        Session.Item("Script") = ""
        Response.Redirect("~/Page2.aspx")

    Else

        Dim sbScript As StringBuilder = New StringBuilder()
        sbScript.AppendLine("( function () {   window.history.pushState(window.history.state, " &
                            " 'Not allowed', " &
                            " 'https://yourdomain.com/page2.aspx'); }()); ")

        ScriptManager.RegisterStartupScript(Me,
                                            Me.GetType(),
                                            "PopUp",
                                            "<script type='text/javascript'>" & sbScript.ToString & "</script>",
                                            False)

    End If

End Sub

However make all control validation by Javascript if it is possible as Client side have more control on Browser than Server side

Browser back button loads old page with old javascript

1 Answers