VB.net autofill form using webkit.net

Question

I've been trying to fill out web forms automatically using a custom made vb.net application, which has been working out perfectly fine for me.

When I went to try to do the same thing with a different website, which only supports IE9+, Chrome and Firefox, it suddenly became an issue. I then tried to download webkit.net, but was then struck by a new issue. The code that used to work using the default vb.net browser, doesn't work with the webkit.net browser.

VB.Net browser autofill form code

            Dim Elements As HtmlElementCollection = Browser.Document.All
            Browser.Document.GetElementById("user").SetAttribute("value", Username)
            Browser.Document.GetElementById("pass").SetAttribute("value", Password)
            Browser.Document.GetElementById("submit").InvokeMember("click")

I am hit by the following errors:

1. 'All' is not a member of 'WebKit.DOM.Document'.
2. 'InvokeMember' is not a member of 'WebKit.DOM.Element'.