[RESOLVED] URLReferrer and Object not set problem

[Krenshau]

Hello,

I am creating a message page that displays a message, then returns the user to the referrer, but I am having a problem.

The error I get is that an object reference is not set. Is there a problem getting the referrer in the page load event?

Here is my code.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
        Me.lblMessage.Text = Page.Request.QueryString("Message").ToString
 
        Dim GotoURL As String
 
        If Not Page.Request.UrlReferrer Is Nothing Then
            GotoURL = Page.Request.UrlReferrer.AbsoluteUri
        Else
            GotoURL = Page.Request.UrlReferrer.ToString <---- Error on this line
        End If
 
        Page.Response.AppendHeader("Refresh", "5; url=" & GotoURL)
 
    End Sub

I understand the error(I think), but I am not sure how that applies in this situation, or how to fix it. I should also mention that I am passing a variable thru the querystring to this page. Would that affect it?

BTW, I found this code on this site while I was searching for a solution. I originally just had the Page.Response.UrlReferrer.ToString.

[Krenshau]

Any ideas? This is VB 2005 for ASP .NET 2.0.

[brucevde]

The Else code will execute if the UrlReferrer IS Nothing. You can't call a method of something that doesn't exist.

[Krenshau]

Ok, thank you brucevde. That is one of those "DUH" things on my part. I should have been able to put that together. However, that still leaves me with the other question. Can I get the URLReferrer in the load event? Basically, you probably can tell what I am trying to do, but is it possible to append the header with the URLReferrer in the page load event, or should I be doing this differently? If differently, how?

Thank you for your help.

[Fishcake]

In which case your code looks fine if you just remove the else part.

So the question is what do you want to happen if there is no referrer?

[Fishcake]

Out of interest why are you sending someone back to the page they last came from?

[Krenshau]

But, there is a referrer. If I pass a variable thru the query string to the message page, there has to be a referrer, else there would be no message to display, and the page wouldn't be called.

I have a profile page that allows the user to edit their profile. If there is a problem, then the user is sent to the message page, which will display a message passed from the previous page thru the query string. In the page load event I pull the message from the URL, display it in the label, then append the header to refresh back to the previous page after five seconds.

Am I misunderstanding how the referrer works here? I thought I understood it, but I am fairly new to .NET and ASP .NET.

Thank you for your help.

[Fishcake]

Ok so in your case you will always have a refferer.

So if your code now looks like below it should work.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
        Me.lblMessage.Text = Page.Request.QueryString("Message").ToString
 
        Dim GotoURL As String
 
        If Not (Page.Request.UrlReferrer Is Nothing) Then
            GotoURL = Page.Request.UrlReferrer.AbsoluteUri           
        End If
 
        Page.Response.AppendHeader("Refresh", "5; url=" & GotoURL)       
 
    End Sub

[Krenshau]

That worked, but I don't understand why.

What is teh difference between:

GotoURL = Page.Request.UrlReferrer.ToString

and

GotoURL = Page.Request.UrlReferrer.AbsoluteUri

Thank you for your help.

[Krenshau]

I spoke to soon, it took me to the message page, which is correct, but now it just refreshes the same page, it doesn't take me back to the previous page.

[Fishcake]

That worked, but I don't understand why.

What is teh difference between:

GotoURL = Page.Request.UrlReferrer.ToString

and

GotoURL = Page.Request.UrlReferrer.AbsoluteUri

Thank you for your help.

In terms of what they return there is no difference.

[Fishcake]

I spoke to soon, it took me to the message page, which is correct, but now it just refreshes the same page, it doesn't take me back to the previous page.

I presume that's because GotoURL isn't getting set so it's refreshing the same page.

Have you tried stepping through your code? Can you post your code as it should work.

[Krenshau]

Yep, that is it. I put another label on the page and if it went into the if statement it would put GotoURL in the label, but it is just blank.

I am not sure what you mean about posting my code as it should work. The code in the message page was changed to what you posted, I am deliberatly creating errors in my profile page so I can test this message page.

I did try changing the Page.Request.UrlReferrer.AbsoluteUri to Page.Request.UrlReferrer.ToString at first because I thought it might have been the problem, but other than that I am not sure what do do since it thinks the referrer is nothing.

[brucevde]

I found this on DevX that might help you...

http://www.devx.com/vb2themax/Tip/18...ticle&trk=MSCP

[Krenshau]

I think I found what my problem is, and what I am doing won't work according to this.

http://msdn.microsoft.com/library/de...s/referrer.asp

My site is using SSL, which, if I understand that article correctly, referrers don't work in SSL. So, I guess I will have to find a different way. I am doing some checking on it now, but if anyone has any suggestions as to how I can do this, I would be grateful.

Thank you for the help.

[Krenshau]

Nevermind, I don't know why I didn't think of it earlier. I got it to work with session variables.

Thank you all very much for your help.

[Fishcake]

You're welcome and yep referrer returns a blank string when coming from a secure page.