.Net - WebClient or HttpWebRequest to get content

I developed an application to download multiple images from a website with a pattern, using a WebClient. When I started with this, my idea was a fast and easy app, so I made a form with:

• WebBrowser (WB)
• Multiline textbox to put multiple urls to crawl
• Listbox to storage the link of each photo
• Textbox to select a targetpath
• Button to start the process

It was easy, I just needed to find the labels of each photos using For + HtmlElement + WB.Document.All. Once I got all links, I used a WebClient to download them very fast (Client.DownloadFile(path, filename)). It works flawlessly.

Now the app is bigger, it has more websites to crawl and I would like to use BackgroundWorker to manage this. I started to learn how BGWorker works, and I noticed that I caot use a Control like WebBrowser, it gives an exception, so I caot use WB.Document.All to get the links.

I found an amazing example in Codeproject of how to download a file with BGWorker, this one concretely:

http://www.codeproject.com/Articles/17979/Downloading-Files-in-NET-With-All-Information-Prog

He uses HttpWebRequest, which seems harder to implement if I first need to get the links.

My question is: Should I recode the app to use HttpWebRequest or can I adapt the current code (WebBrowser implicated) to use a BGWorker? If it's possible to use WebBrowser with BGWorker, which one is the correct way to make it?

My current relevant code (I call this function when I click the button). I put the necessary lines only:

Function ExtractLicensePlate()
        Dim Client As New WebClient
        Dim totalPhotos As Integer = 0
        Dim finalPlate As String = "[no licenseplate found]"
        Dim totalCarsList As Integer = txtURLs.Lines.Where(Function(l) Not String.IsNullOrWhiteSpace(l)).Count()

    For i = 0 To totalCarsList - 1
        WB.Navigate(txtURLs.Lines(i))
        WaitForPageLoad()

        For Each ele As HtmlElement In WB.Document.All
            'ALD
            If comboProviders.SelectedIndex = 0 Then
                If ele.GetAttribute("src").ToLower.Contains("iddoc") Then
                    Dim imgsrc As String = ele.GetAttribute("src")
                    lstPhotos.Items.Add(imgsrc)
                End If
                'get license plate to make folders
                If ele.GetAttribute("action").ToLower.Contains("matr=") Then
                    Dim fullURLname As String = ele.GetAttribute("action")
                    finalPlate = fullURLname.Split("=")(3).Substring(0, 7)
                End If
            End If
        Next

        If (Not Directory.Exists(txtDirectory.Text & "" & finalPlate)) Then
            If Not (finalPlate = "[no licenseplate found]") Then
                Directory.CreateDirectory(txtDirectory.Text & "" & finalPlate)
            End If
        End If

        For j = 0 To lstPhotos.Items.Count - 1
            Client.DownloadFile(lstPhotos.Items(j).ToString, txtDirectory.Text & "" & finalPlate & "" & finalPlate & j & ".jpg")
            Client.Dispose()
        Next j
        lstPhotos.Items.Clear()
    Next i
    Return 0
End Function

Any help will be very appreciate.

Thanks to everyone.