Accessing document elements when using Windows.Forms.WebBrowser - winforms

Question

I'm new to automating webpage access, so forgive what is probably a remedial question. I'm using C#/Windows.Forms in a console app. I need to programmatically enter the value of an input on a webpage that I cannot modify and that is running javascript. I have successfully opened the page (triggering WebBrowser.DocumentCompleted). I set browser emulation mode to IE11 (in registry), so scripts run without errors. When DocumentCompleted() triggers, I am unable to access the document elements without first viewing the document content via MessageBox.Show(), which is clearly not acceptable for my unattended app.
What do I need to do so that my document elements are accessbile in an unattended session (so I can remove MessageBox.Show() from the code below)? Details below. Thank you.
The input HTML is:
<input class="input-class" on-keyup="handleKeyPress($key)" type="password">
My DocumentCompleted event handler is:
private static void LoginPageCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
WebBrowser wb = ((WebBrowser)sender);
var document = wb.Document;
// I'm trying to eliminate these 3 lines
var documentAsIHtmlDocument = (mshtml.IHTMLDocument)document.DomDocument;
var content = documentAsIHtmlDocument.documentElement.innerHTML;
MessageBox.Show(content);
String classname = null;
foreach (HtmlElement input in document.GetElementsByTagName("input"))
{
classname = input.GetAttribute("className");
if (classname == "input-class")
{
input.SetAttribute("value", password);
break;
}
}
}

Answer 1

The problem for me was that the page I'm accessing is being created by javascript. Even though documentComplete event was firing, the page was still not completely rendered. I have successfully processed the first page by waiting for the document elements to be available and if not available, doing Application.DoEvents(); in a loop until they are, so I know now that I'm on the right track.
This SO Question helped me: c# WebBrowser- How can I wait for javascript to finish running that runs when the document has finished loading?
Note that checking for DocumentComplete does not accurately indicate the availability of the document elements on a page generated by javascript. I needed to keep checking for the elements and running Application.DoEvents() until they became available (after the javascript generated them).

Answer 2

If the problem comes from the creation of a STAThread, necessary to instantiate the underlying Activex component of WebBrowser control, this is
a modified version of Hans Passant's code as shown in the SO Question you linked.
Tested in a Console project.
class Program
{
static void Main(string[] args)
{
NavigateURI(new Uri("[SomeUri]", UriKind.Absolute), "SomePassword");
Console.ReadLine();
}
private static string SomePassword = "SomePassword";
private static void NavigateURI(Uri url)
{
Thread thread = new Thread(() => {
WebBrowser browser = new WebBrowser();
browser.DocumentCompleted += browser_DocumentCompleted;
browser.Navigate(url);
Application.Run();
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
}
protected static void browser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
WebBrowser browser = ((WebBrowser)sender);
if (browser.Url == e.Url)
{
while (browser.ReadyState != WebBrowserReadyState.Complete)
{ Application.DoEvents(); }
HtmlDocument Doc = browser.Document;
if (Doc != null)
{
foreach (HtmlElement input in Doc.GetElementsByTagName("input"))
{
if (input.GetAttribute("type") == "password")
{
input.InnerText = SomePassword;
//Or
//input.SetAttribute("value", SomePassword);
break;
}
}
}
Application.ExitThread();
}
}
}