async Task <XmlDocument> GetExplainDomAsync(string name, string type, string expainUrl) { // 先看看缓存文件是否存在 string cacheFileName = MakeCacheFileName(name, type); if (File.Exists(cacheFileName)) { XmlDocument result = new XmlDocument(); result.Load(cacheFileName); return(result); } else { var download_result = await WebClientEx.DownloadStringAsync(expainUrl).ConfigureAwait(false); File.WriteAllText(cacheFileName, download_result.String, download_result.Encoding); XmlDocument result = new XmlDocument(); result.LoadXml(download_result.String); return(result); } }