Codebehind for the mainpage of my application

MainPage.xaml.cs

private void WebView_OnNavigating (object sender, WebNavigatingEventArgs e)
{
    var url = e.Url.ToLowerInvariant ();

    if (url.Contains ("thirdparty.com") || url.Contains ("vimeo.com") || url.Contains ("bid.g.doubleclick.net")) {
        // Do nothing, links are loaded as embedded
    } else if (url.StartsWith ("https://getmypdfurl.com", StringComparison.Ordinal)) {
        e.Cancel = true;

        if (Device.OS == TargetPlatform.Windows)
            Device.OpenUri (new Uri (e.Url));
        else
            Navigation.PushAsync (new ShowPdfPage (e.Url));
    } else if (!url.StartsWith ("https://ourwebapplication.com", StringComparison.Ordinal)) {
        e.Cancel = true;

        if (Device.OS == TargetPlatform.iOS) {
            try {
                DependencyService.Get<IWebBrowserService> ().OpenUrl (e.Url);
            } catch {
                Device.OpenUri (new Uri (WebUtility.UrlDecode (e.Url)));
            }

            return;
        }

        Device.OpenUri (new Uri (WebUtility.UrlDecode (e.Url)));
    }
}