I think I am approaching the solution of my problem. I hope that this is my last question but can you tell me how to make sure that there is not an existing field in the keys collection. You can see my code below but some keys like the language and tabid exists two times in my URL.

Dim NewQuery As String = ""

For Each key In Request.QueryString.Keys

    Dim Value As String = Request.QueryString(key)

    NewQuery &= "&" & key & "=" & Value

Next

Dim URL As String = NavigateURL(TabId, "", NewQuery)

I know how to check the duplicated values in my code. The problem is that I have to check all the keys including the keys that DNN creates. Some Keys like tabid and language are keys which are used by the DNN framework. Even when I make the check for the keys that I get inside the loop, the tabid and language are included twise. The first appearance caused by me and the other by the DNN framework. In order to make the check I added the X character in front of the key and its value in order to know which key is created by me and which by the DNN. So when I have the following URL:

http://localhost/dnndevelopement/stats2/tabid/75/language/en-US/ProductID/12/Default.aspx

The generated url by my code is the following:

http://localhost/dnndevelopement/stats2/tabid/75/XTabId/X75/Xlanguage/Xen-US/XProductID/X12/language/en-US/Default.aspx

Now you will see that TabID exists 2 times in the generated URL. The first has not the X character in front of its name which means that it is automatically generated by the DNN framework and the other has the X Character which tells me that I created this key.

So I have to find a way to check if a key is used by DNN framework. I cannot assume that tabid and language is used by dnn because it does not used all the time. For example language is used only when we have Multilanguage pages in our site. There are also some other keys which are used by dnn in various occasions. If I remember well the PortalID or something like this is used when we have multiple portals.

Sometimes I wonder why a small number of lines of code cause me to spend so many hours in front of my laptop trying to find a solution. I started a new search from the beginning spending some time trying to find all the different ways of getting information about the current url. After combining various properties, I created the following code in order to get the URL of the current page.

Dim CurrentURL As String = ""

If (Request.IsSecureConnection) Then

    CurrentURL = "https://" & Request.Url.Host & Request.RawUrl

Else

    CurrentURL = "http://" & Request.Url.Host & Request.RawUrl

End If

I suppose that DNN development team should create a property which will give this information to the module developers.

I would like to thank everyone who replied to this thread.