Getting the UrlReferrer 1

[ericnet]

When I run this code:

  Response.Write("<p>UrlReferrer:</p>")
  If Request.UrlReferrer Is DBNull.Value Then
   Response.Write("UrlReferrer = Bookmark" & "<br>")
  Else
   Response.Write("UrlReferrer = " & Request.UrlReferrer.ToString() & "<br>")
  End If

I get this error:
System.NullReferenceException: Object reference not set to an instance of an object.
Line 38: Response.Write("UrlReferrer = " & Request.UrlReferrer.ToString() & "<br>")

How can I solve it?

Thanks

 

[ca8msm]

That's because the Request.UrlReferrer won't be equal to DBNull.Value. Try changing it to:

If Request.UrlReferrer Is Nothing Then

As a side note, the user may not have necessarily come from a "bookmark" just because the referrer is null. Also, you shouldn't be using Response.Write (unless you are just testing of course).


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[ericnet]

Yes, in this way it works! :

If Request.UrlReferrer Is Nothing Then

Thank you

As a side note, the user may not have necessarily come from a "bookmark" just because the referrer is null.

Ok. Then the value can be also null, so perhaps it is better that I check for both values (nothing and null) before I want to store the value into the DB..

If Request.UrlReferrer Is Nothing Or Request.UrlReferrer Is DBNull.Value Then

  Dim ref As String = DBNull.Value
  'Then insert that null value into the DB

Else
  Dim ref As String = Request.UrlReferrer.ToString()
  'Then insert that value into the DB 
End If

What do you think? This will prevent of any other error related to 'Request.UrlReferrer' value?

Also, you shouldn't be using Response.Write (unless you are just testing of course).

Yes, I'm testing

 

[ca8msm]

Ok. Then the value can be also null, so perhaps it is better that I check for both values (nothing and null) before I want to store the value into the DB..

Sorry, I didn't mean "null". What I meant was that just because a referrer doesn't exist (i.e. it is Nothing) that doesn't mean that they have come from a bookmark. For example, they may have searched for your site and typed the address into the address bar.


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[ericnet]

Ok. But I really need to know if there is the possibility of any other error due to 'Request.UrlReferrer' value, like I mentioned in my original post (NullReferenceException or others) that you solved it. Because when I publish my website I want to avoid the pages are not displayed due to these errors.

Indeed I have the same doubt about the possible errors that can be thrown due to the type of values of these ‘Requests’ can contain:

UserHostAddress:
Request.UserHostAddress

UserAgent:
Request.UserAgent

Requested URL:
Request.Url.ToString


-Browser capabilities-
Dim bc As HttpBrowserCapabilities = Request.Browser
Crawler:
bc.Crawler
Name:
bc.Browser
Version:
bc.Version
JavaScript enabled:
bc.JavaScript
Cookies enabled:
bc.Cookies