Public Sub NavigateToString ( _
    text As String _
)

Dim instance As WebBrowser
Dim text As String

instance.NavigateToString(text)

public void NavigateToString(
    string text
)

public:
void NavigateToString(
    String^ text
)

public function NavigateToString(
    text : String
)

You cannot use methods in XAML.

private void goNavigateToStringButton_Click(object sender, RoutedEventArgs e)
{
  // Load HTML document as a string
  Uri uri = new Uri(@"pack://application:,,,/HTMLDocumentWithoutScript.html", UriKind.Absolute);
  Stream stream = Application.GetResourceStream(uri).Stream;
  using (StreamReader reader = new StreamReader(stream))
  {
    // Navigate to HTML document string
    this.webBrowser.NavigateToString(reader.ReadToEnd());
  }
}