public override void ViewDidLoad()
{
base.ViewDidLoad();
Title.Text = Announcement?.Title;
Subtitle.Text = string.Format("{0} 发布于 {1}", Announcement?.Owner?.Name, Announcement?.CreatedAt);
var contentDir = Path.Combine(NSBundle.MainBundle.BundlePath, "Content/");
var html = Announcement?.Body?.WrapWithCss(cssFile);
Webview.LoadHtmlString(html, new NSUrl(contentDir, true));
}