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I have an old application which has numerous webforms. On every aspx page there is a designated back button, which takes the user to the previous page. All the buttons have the javascript onclick event set to history.back().

On one of the aspx pages, the back button would not work at all. We decided to use a server side button that would accomplish the same thing. The onclick event of the button has the necessary code to take the user to previous page.

First I created the onclick event in the following way, but the back button did not work at all. When I went in the debug mode, I found that the prevPage variable was holding the current page URL instead of the previous page URL.

private void btnBack_Click(object sender, System.EventArgs e)
{
    string prevPage = Request.UrlReferrer.ToString();
    Response.Redirect(prevPage);
}

Then I changed the prevPage to a static variable and defined its value to be set inside the if(!IsPostBack) block. Now the back button worked correctly. 

static string prevPage = string.Empty;
private void Page_Load(object sender, System.EventArgs e)
{
    if(!IsPostBack)
    {
        prevPage = Request.UrlReferrer.ToString();
    }
}

private void btnBack_Click()
{
    Response.Redirect(prevPage);
}

I did not understand why the first attempt wouldn't work and why second attempt would.

I have a feeling that this might explain if there is something else going on with this particular page that would also not let the history.back() or history.go(-1) work.

Can you please provide some insight into this?

Edit: I am using IE8.

Darren
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Animesh
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  • use Firebug and see what is happening with history – Antonio Bakula Aug 17 '12 at 10:18
  • I have not much exposure to firebug other than checking the html/css of a webpage. Would you mind telling me what I would do check what's happening with the history? – Animesh Aug 17 '12 at 10:28
  • Instead of history.back() do simple javscript function : function GoBack() { history.back(); } , call that in onClick method, then in firebug script tab put breakpoint and inspect history object. That is first step to inspect what is happening. – Antonio Bakula Aug 17 '12 at 10:32
  • Interestingly, in Firefox the back button is working as it should. I am doing the same exercise in Developer Tools in IE8. – Animesh Aug 17 '12 at 10:53
  • I have not been able to track the history object, in developer tools of IE8. Thank you for showing this method of debugging. I will continue the investigation. – Animesh Aug 17 '12 at 11:22

3 Answers3

4

The first attempt would not work because when you click the button the post back has already occurred, therefore the Referrer URL is the one coming from the button (The page you are on).

In my opinion I would not send a request to the server to push the page back a level, it's an unnecessary request when it could be achieved quicker on the client side.

Darren
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  • I agree to this completely. It is a waste of a request when it can be dealt with on the client side. However, so far I have not been able to figure why the client side method wouldn't work for this page. So I wanted to incorporate the server-side method since it is just one aspx page. – Animesh Aug 17 '12 at 10:31
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Man, DO NOT use static variable to store previous URL. It will be shared among all sessions and if case when your page can be achieved from different places, users will be confused. If you want to track last page, Session is your best friend.

the_joric
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  • What you have mentioned is a very valid concern. Indeed this page can be accessed from multiple pages and reports. I would switch to using Session instead. Thanks for the tip. – Animesh Aug 17 '12 at 10:40
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JavaScript:window.history.go(-2);return false;

That is all you need, put that in a onclientclick or simply in an anchor tag. You need two clicks because the first click will take you to a confirm submission page.

TGarrett
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