Return to calling page

**gringo** · 03-06-2006, 06:23 AM

Hi,

I have a page on which there is a login button. The user clicks the login button and is transferred to the login page. After logging on, I want the user to be returned to the original page (as happens in this forum). How would I do this?

One method I can think of is to pass as a parameter the calling page and then response.redirect back to it, but I'd prefer to use some kind of 'RETURN' function. Does one exist? Is this the best way?

**sdcdesign.co.uk** · 03-06-2006, 11:10 AM

The way this website does it is if the user is not logged in, they are sent to login.php with the querystring having the page they were viewing. This is the easiest and most common way to do it.

But the way you want to, think about it, after they have logged on, they will be sent back to the login page (unless you are using PagePostBack).

To get the referring page:

Code:

Request.ServerVariables["HTTP_REFERRER"];

**gringo** · 03-06-2006, 12:23 PM

Right OK, so it sounds like manually retrieving the refferring page is neater than passing parameters. I'll have a play with that.

Thanks!

**Minaki** · 03-07-2006, 04:32 AM

Look up Forms Authentication.

Basically you set your web.config up to tell ASP.NET you're using forms authentication, which pages/directories to protect, and which page to use as your login page.

When users try to access a page which is listed as protected in web.config, they are redirected automatically to the login page you specified. In the login page you then just need to perform the authentication and then call FormsAuthentication.RedirectFromLoginPage() to redirect the user to the page they origionally requested.

**gringo** · 03-07-2006, 06:35 AM

Thanks Minaki. I thought about that but it didn't seem to fit what I wanted to do.

I wanted something similar to a forum where you can view the same page in 2 different modes - logged in and not logged in. The different modes allow you to do different things. So it wasn't so much a case of protecting certain pages/directories as allowing certain functionality on those pages - I don't think I can do that with forms authentication, can I?

**Minaki** · 03-07-2006, 08:02 AM

You can still use Forms Authentication, but you will need to leave the pages unprotected and programatically restrict access to the functions. The Login button on the pages could link to the login.aspx page, passing the ReturnURL query string - this is what FormsAuthentication.RedirectFromLoginPage uses. (It also handles messy things like your cookies for you)

**gringo** · 03-07-2006, 10:12 AM

OK, I'll have a look at forms authentication when I get the chance, ta.

**gringo** · 03-14-2006, 04:34 PM

I've tried the following code but it returns the error "Value cannot be null. Parameter name: url" when I click the button.

HTML Code:

<%@ Debug="true" %>
<script runat="server">

Dim Referrer as String

    Dim greeting as String
       Sub Page_Load
       If Not IsPostback Then
         If Not Request.UrlReferrer Is Nothing Then
 	   Referrer = Request.urlreferrer.ToString()
 	 Else
 	   Referrer = "otherpage.aspx"
 	 End If
       End If
       End Sub
    
       Sub btnClick(Sender as Object, e as EventArgs)
         Response.Redirect(Referrer)
       End Sub

</script>
<html>
<head>
    <title>Testing asp.net</title>
</head>
<body>
    <form runat="Server">
        <asp:Button id="Button1" onclick="btnClick" Text="redirect" Runat="Server"></asp:Button>
    </form>
</body>
</html>

Somehow, the value of Referrer is becoming null between the page loading and the btnClick routine executing. I thought declaring that variable globally would retain its value. Does anybody know what I'm doing wrong?