How do I expose the LoadCompleted method in the WebBrowser class in WPF C#?

I am trying to write a C# program in wpf that retrieves the content of a web page.

The first thing I tried was to try the WebRequest and WebResponse classes. This did not provide the actual displayed content. WebResponse reveils the HTML code that is sent to the browser. But I discovered that, while the page is being loaded by the browser, javascript can change what content is finally displayed in the browser.

So I decided to use the WebBrowser class.

Immediately I found that there are two WebBrowser classes. Thee is the one that is documented for WinForms and there is another that is documented for WPF. I need to understand the one documented for WPF. What I think I neeed to know what to do is to retrieve code after the "LoadCompleted" method is caused. But I do not know how to this and I cannot find any example demonstrating how this is done.