how to expired previous page when we click on back button in asp.net

how to expired previous page when we click on back button in asp.net
TUS11Asked:
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Roman GhermanSenior Software EngineerCommented:
You need to put nocache

------------------------
You can find me on: http://extremedev.blogspot.com
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Roman GhermanSenior Software EngineerCommented:
uuups,

Forgot to add the code:
<% System.Web.HttpContext.Current.Response.AddHeader( "Cache-Control","no-cache")
System.Web.HttpContext.Current.Response.Expires = 0
System.Web.HttpContext.Current.Response.Cache.SetN oStore()
System.Web.HttpContext.Current.Response.AddHeader( "Pragma", "no-cache")%>

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Put that on the top of the aspx page or on code behind.
This will make the page not to be cached and when clicking back button in browser - it will not have anything to display except Web page expired.

------------------------
You can find me on: http://extremedev.blogspot.com
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TUS11Author Commented:
Hi,
  i add the above code on page load of the first page and when i redirect to second page from the first page then if i use the back button  on second page then it does not expired page message. it show the first page.


Please help me bcoz it is urgent for me.


Thanks
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Todd GerbertIT ConsultantCommented:
Setting these seems to work in a quick test for me:

Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();

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Keep in mind, though, that ultimately it's up to the web browser and there is no guarantee that the browser will honor the cache control headers.
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Roman GhermanSenior Software EngineerCommented:
OK,

It looks like this only works if the connection is secure: https.

Otherwise you will have to use session variables and when navigate away then delete the variable from the session.

In codebehind check if page had "expired" - using the Session Variable then Redirect to a Web Page Expired page (a simple html page which you will have to create).

You will also set this:
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();

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In order for page to make a postback when you click back button, so that you will be able to do your check on codebehind.

------------------------
You can find me on: http://extremedev.blogspot.com
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TUS11Author Commented:
Hi,

All above solution not working for me.
we are using http not https then in this case what i do for expiring the page.
Please help me.

Thanks
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Todd GerbertIT ConsultantCommented:
What browser are you using, which version of the .Net Framework, what code in your ASPX page, and how are you determining that the page is still being cached?
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TUS11Author Commented:
hi,
    I am using IE8, 2.0 .net framework.
    and in code behind of ASPX page i am using this below code on page load.
System.Web.HttpContext.Current.Response.AddHeader( "Cache-Control","no-cache")
System.Web.HttpContext.Current.Response.Expires = 0
System.Web.HttpContext.Current.Response.Cache.SetN oStore()
System.Web.HttpContext.Current.Response.AddHeader( "Pragma", "no-cache")

For checking the page expiry i have the two page.
On first page i have a button which id redirected to the second page but i want that when we press BACK button then first page should be show the Page Expiry warning message.
and the above code i add on the first page .


Thanks
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Todd GerbertIT ConsultantCommented:
You will only get the warning message you're describing if the expired page was retrieved as a result of a POST operation, not a GET.

e.g. Default.aspx has a button with it's PostBackUrl set to Default2.aspx, the user clicks the button (this causes the ASP.Net form to POST to Default2.aspx).  Default2.aspx sets no-cache; user navigates from Default2.aspx to Default3.aspx.  User clicks back button, content expired message is displayed.

However, if Default.aspx has a normal <a href="Default2.aspx">Link</a> link to Default2.aspx, when the user clicks it a GET will be used to retrieve Default2.aspx.  If the user naviages to Default3.aspx and then uses the back button, no warning message will be seen (because there was no POST data to have expired).

Default1.aspx:
<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
		Click this link to GET Default2.aspx: <a href="Default2.aspx">Get Default2.aspx</a><br />
		<br />
		Click this button to POST form results to Default2.aspx:
		<asp:Button ID="SubmitButton" runat="server" Text="POST to Default2" PostBackUrl="~/Default2.aspx" />
    </div>
    </form>
</body>
</html>

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Default2.aspx
<%@ Page Language="C#" %>
<%@ PreviousPageType VirtualPath="~/Default.aspx" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
	private void Page_Load(object sender, EventArgs e)
	{
		Response.Cache.SetCacheability(HttpCacheability.NoCache);
		Response.Cache.SetNoStore();
	}
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <a href="Default3.aspx">test</a>
    </div>
    </form>
</body>
</html>

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Default3.aspx
<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
    </div>
    </form>
</body>
</html>

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tgerbert-435717.flv
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TUS11Author Commented:
Please cancel this request
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TUS11Author Commented:
I've requested that this question be closed as follows:

Accepted answer: 0 points for TUS11's comment http:/Q_26897839.html#35189676

for the following reason:

OK solution
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Todd GerbertIT ConsultantCommented:
I think http:Q_26897839.html#a35195100 adequately demonstrates how to force a page to expire, complete with code and a screencast.
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