[英]WebApi and async methods
我非常迷失于.NET中的新异步方法。 我的问题是我有方法
private static List<RouteDTO> ParseRoutesHTML(string result, Cookie cookie)
{
List<RouteDTO> routes = new List<RouteDTO>();
HtmlDocument htmlDocument = new HtmlAgilityPack.HtmlDocument();
htmlDocument.LoadHtml(result);
int contNumber = 1;
while (true)
{
HtmlNode divNode = htmlDocument.GetElementbyId("cont"+contNumber);
if (divNode != null)
{
HtmlNode table = divNode.SelectSingleNode("table");
if (table != null)
{
string fullRoute = "";
HtmlNodeCollection dataRows = table.SelectNodes("tr[@align]");
RouteDTO currentRoutes = new RouteDTO();
foreach (var dataRow in dataRows)
{
currentRoutes.routes.Add(ParseRouteDataRow(dataRow));
//fullRoute+=ParseDataRow(dataRow)+" then ";
}
HtmlNodeCollection lastRow = table.SelectNodes("tr").Last().SelectSingleNode("td/div").SelectNodes("a");
HtmlNode mapLink = lastRow[1];
ParseMap(currentRoutes, mapLink);
HtmlNode priceLink = lastRow[2];
string priceHref = priceLink.Attributes["href"].Value;
ParcePrice(currentRoutes, priceHref, cookie);
routes.Add(currentRoutes);
}
contNumber++;
}
else
{
break;
}
}
return routes;
}
private static void ParcePrice(RouteDTO currentRoutes, string priceHref, Cookie cookie)
{
var cookieContainer = new CookieContainer();
var handler = new HttpClientHandler() { CookieContainer = cookieContainer };
var httpClient = new HttpClient(handler);
cookieContainer.Add(cookie);
var priceMessage = httpClient.GetByteArrayAsync("http://razpisanie.bdz.bg" + priceHref).Result;
var priceResponse = Encoding.UTF8.GetString(priceMessage, 0, priceMessage.Length - 1);
var priceInfo = ParsePriceResponse(priceResponse);
currentRoutes.priceInfo = priceInfo;
}
private static void ParseMap(RouteDTO currentRoutes, HtmlNode mapLink)
{
var httpClient = new HttpClient();
string mapHref = mapLink.Attributes["href"].Value;
var mapMessage = httpClient.GetByteArrayAsync("http://razpisanie.bdz.bg" + mapHref).Result;
var mapResponse = Encoding.UTF8.GetString(mapMessage, 0, mapMessage.Length - 1);
string mapString = ParseMapResponse(mapResponse);
currentRoutes.imageBase64 = mapString;
}
请不要介意糟糕的HTML解析(网站本身很糟糕),但请看一下ParseMap和ParsePrice方法。 这些发出Web请求,因此需要异步。 问题是,如果我使它们异步,恐怕在调用return routes
时它们将不会完成(这实际上是在使void异步时发生的情况,但我发现这是大不了)。 如何使return routes
在调用之前等待所有异步方法完成?
从每个解析方法返回Task,将它们放在列表或数组中,然后使用Task.WhenAll创建一个任务,该任务将在所有任务完成后完成,并从操作中返回。
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