Auto Website Login: SetAttribute not working - vb.net

Question

I'm creating a program dashboard and one feature is that the user is automatically logged into a website site using stored credentials in the program (no need to open chrome or FF).
In the program, await task delay is working, I see the username and password fields populate before submission (click), but when it tries to submit, the browser, built into the form, acts like the page is empty and no credentials have been entered? I should mention that I can see the username and password entered in the form, but the page acts like nothing has been entered. What am I doing wrong here?
Side note: The button on the site we're connecting to doesn't have an element ID, only a type is shown...hence the workaround for Invokemember("Click")
Any help is appreciated.
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Label3.Visible = False
End Sub
Private Function login_thesite() As Task
WebBrowser1.Document.GetElementById("username").SetAttribute("value", "Username")
WebBrowser1.Document.GetElementById("Password").SetAttribute("value", "Password")
Dim allelements As HtmlElementCollection = WebBrowser1.Document.All
For Each webpageelement As HtmlElement In allelements
If webpageelement.GetAttribute("type") = "submit" Then
webpageelement.InvokeMember("click")
End If
Next
End Function
Private Property pageready As Boolean = False
#Region "Page Loading Functions"
Private Sub WaitForPageLoad()
AddHandler WebBrowser1.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf PageWaiter)
While Not pageready
Application.DoEvents()
End While
pageready = False
End Sub
Private Sub PageWaiter(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs)
If WebBrowser1.ReadyState = WebBrowserReadyState.Complete Then
pageready = True
RemoveHandler WebBrowser1.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf PageWaiter)
End If
End Sub
#End Region
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If CheckBox1.Checked = True Then
login_thesite()
WaitForPageLoad()
End If
End Sub
Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
TextBox1.Text = ""
TextBox2.Text = ""
Label3.Visible = True
WebBrowser1.Navigate("https://thesite.com/#/login")
WaitForPageLoad()
End Sub
End Class

Answer 1

You don't need any async procedure here. The WebBrowser.DocumentCompleted event is already invoked asynchronously. DoEvents() is equally useless if not disruptive.
You just need to subscribe to the DocumentCompleted event and call the Navigate method to let the WebBrowser load the remote Html resource.
When the HtmlDocument is finally loaded, the WebBrowser will signal its completion setting its state to WebBrowserReadyState.Complete.
About the Html Input Element and Forms:
here, the code is supposing that there's only one Form in that HtmlDocument.
It may be so, but it may be not. A Html Document can have more than one Form and each Frame can have its own Document. IFrames will have one each for sure.
Read the notes in this answer (C# code, but you just need the notes) for more information on how to handle multiple Frames/IFrames
Button1 will wire up the DocumentCompleted event and call Navigate().
When the Document is completed, the code in the event handler will run and perform the LogIn procedure.
The event handler is then removed, since it has complelted its task and you still need to use the WebBrowser for other purposes.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Button1.Enabled = False
WebSiteLogIn()
End Sub
Private Sub WebSiteLogIn()
AddHandler WebBrowser1.DocumentCompleted, AddressOf PageWaiter
WebBrowser1.Navigate("https://thesite.com/#/login")
End Sub
Private Sub PageWaiter(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs)
If WebBrowser1.ReadyState = WebBrowserReadyState.Complete Then
WebBrowser1.Document.GetElementById("username").SetAttribute("value", "Username")
WebBrowser1.Document.GetElementById("Password").SetAttribute("value", "Password")
Dim allInputElements = WebBrowser1.Document.Body.All.
Cast(Of HtmlElement).Where(Function(h) h.TagName.Equals("INPUT")).ToList()
For Each element As HtmlElement In allInputElements
If element.GetAttribute("type").ToUpper().Equals("SUBMIT") Then
element.InvokeMember("click")
End If
Next
RemoveHandler WebBrowser1.DocumentCompleted, AddressOf PageWaiter
Button1.Enabled = True
End If
End Sub