How to assign HtmlDocument to a web browser, then interact with specific controls via GetElementById in c# / Console application

Question

I have a requirement to navigate to a specific website, select a value from a drop down list, then click on a submit button. The solution has to be via a console app via c#.

So working backwards, I need to eventually be able to interact with controls like this:

html.GetElementById("shellmenu_0").InvokeMember("Click");

In order to work with html elements I need an HtmlDocument object. So as an example, the code below attempts to go to the Microsoft site and click a link to a new page. The code is as follows.

 WebBrowser wb = new WebBrowser();
 wb.AllowNavigation = true;
 wb.Navigate("https://www.microsoft.com/en-us/?ql=4");
 HtmlDocument document = wb.Document;
 document.GetElementById("shellmenu_0").InvokeMember("Click");

I think I am on the right track, but I am hitting a null exception on the document. I must be missing a step to assign the website to the document somehow.

Any advice would be greatly appreciated. Thanks in advance!