private void NavigateContent(string tag) { if (!ContentMap.ContainsKey(tag)) { Debug.WriteLine($"未知的内容: {tag}"); return; } if (NavigateHistory.ContainsKey(tag)) { // has history if (previousTag != null) { // save previous content history NavigateHistory[previousTag] = ContentFrame.GetNavigationState(); } // restore history ContentFrame.SetNavigationState(NavigateHistory[tag]); } else { // navigate to new content ContentFrame.Navigate(ContentMap[tag]); } previousTag = tag; }