vb.net webbrowser documentcompleted event - page not loading - vb.net

Question

I have searched the other questions surrounding the WebBrowser DocumentCompleted event, but no-one seems to have the exact problem that I am having.
I am trying to automate searching flights on an airline website. The first url I use is the same every time except for the date part so it's easy enough to get the WebBrowser to go the URL by combining strings. However, that page is a disclaimer page that has a 'proceed' button that needs to be clicked before prices are shown. If I use a series of buttons on a form, I can get to the first URL by clicking button1, and then click the proceed button by clicking button2. It works fine.
However, I wanted to remove the need to click button2 so attempted to use the WebBrowser DocumentCompleted event. The problem that I am having is that the first page never seems to fully load in the webbrowser and so the button is never clicked.
This is the code that I am using for the two buttons and the DocumentCompleted event
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
TextBox1.Text = fullURL
WebBrowser1.Navigate(fullURL)
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim allElements As HtmlElementCollection = WebBrowser1.Document.All
For Each webpageelement As HtmlElement In allElements
If webpageelement.GetAttribute("src") = proceedbuttonattribute Then
webpageelement.InvokeMember("click")
End If
Next
End Sub
Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
If TextBox1.Text.StartsWith(firstURL) = True Then 'make sure that button is only clicked after first webpage loads
Dim allElements As HtmlElementCollection = WebBrowser1.Document.All
'Click 'Proceed to Booking' button
For Each webpageelement As HtmlElement In allElements
If webpageelement.GetAttribute("src") = proceedbuttonattribute Then
webpageelement.InvokeMember("click")
End If
Next
End If
End Sub
Thanks!

Answer 1

WebBrowser1.Navigate(fullURL)
Do While wb.ReadyState <> WebBrowserReadyState.Complete
Application.DoEvents()
Loop
;)

Answer 2

When you say DocumentCompleted is never triggered, do you mean it isn't triggered at all or are you saying that maybe the If statement isn't returning True, and therefore the contents (and click action) are not run?
Also, are there any frames or iframes on this page? Because, if there are, DocumentCompleted will not run until each and every single frame is loaded and completed, and if its an ajaxed frame, then that will introduce mroe problems. All it takes is for one of the frames to not load properly or remain in "Interactive" mode (where .readystate = 3) instead of it being fully and properly loaded (where .readystate = 4) and this will prevent the DocumentCompleted event from getting triggered.
Also, how long are you waiting for the DC event to trigger?
There is a better way around this, all you need to do is run a Do/While loop, with the exact same code as in your DC event, and it will just sit there (after the .Navigate2 is called) and just wait until that button shows up in the DOM, and as soon as the following returns True, you can use .InvokeMember and click on the button.
If webpageelement.GetAttribute("src") = proceedbuttonattribute Then
So, in this case, you will create another function named "WaitUntilButtonFound" and perhaps place a 100 millisecond Sleep (wait) between each loop, and a .DoEvents (found in .Threading namespace) right after or before the Sleep method (also found in .Threading I think).
This way, as soon as the button of relevance appears in the Document Object Model, you can click it, and if you want, as soon as its found, you can wait another 2 - 3 seconds (if you want, no real need) and then click it. Because finding that button in the DOM is an indicator that the page has either loaded, or partially loaded (where the relevant or necessary part has completed loading), so that you can resume the action you wanted to take on that button (which is, to click it), right after it appears. In fact, it'll be the quickest way to move forward as well.
What do you think? Let me know how you go and if you need more help or guidance. Also, if you could let us know if the DC event is absolutely not being triggered or if it's just your IF statement that is blocking the DC from running the code inside the DC event, that would be helpful, because if the DC event is being triggered but code inside isn't running because of the If statements inside it, that is something entirely different to the DC even not being triggered at all.
Let us know, thanks.