I have some code that lays out like this:
Class1
Task<List<ConfSession>> getSessionsTask = Task.Factory.StartNew(() =>
{
var confSessions =
TaskHelper<ConfSession>.InvokeTaskMagic(request);
//PROBLEM - THIS CODE RACES TO THE NEXT LINE
//BEFORE confSessions IS POPULATED FROM THE LINE ABOVE - IE
//confSessions IS ALWAYS AN EMPTY LIST
//WHEN IT'S RETURNED
return confSessions;
}
);
Class2 (TaskHelper)
//methods
public static List<T> InvokeTaskMagic(HttpWebRequest request)
{
var resultList = new List<T>();
Task<WebResponse> task1 = Task<WebResponse>.Factory.FromAsync(
(callback, o) => ((HttpWebRequest)o).BeginGetResponse(callback, o)
, result => ((HttpWebRequest)result.AsyncState).EndGetResponse(result)
, request);
task1.ContinueWith((antecedent) =>
{
if (antecedent.IsFaulted)
{
return;
}
WebResponse webResponse;
try
{
webResponse = task1.Result;
}
catch (AggregateException ex1)
{
throw ex1.InnerException;
}
string responseString;
using (var response = (HttpWebResponse)webResponse)
{
using (Stream streamResponse = response.GetResponseStream())
{
StreamReader reader = new StreamReader(streamResponse);
responseString = reader.ReadToEnd();
reader.Close();
}
}
if (responseString != null)
{
resultList =
JsonConvert.DeserializeObject<List<T>>(responseString);
}
});
return resultList;
}
TaskHelper是我创建的一个类,旨在标准化我在多个方法中拥有的一堆冗余任务代码。该类仅用于接收HttpWebRequest,使用Task执行它,在ContinueWith块中获取响应,将响应解析为List<T>
,并返回List<T>
。
我在一个任务中包装了Class1对TaskHelper的调用,因为我需要在class1中继续之前从InvokeTaskMagic方法获取结果 (即class1的下一步是使用List<T>
)。正如在代码中的注释中所述,我的问题是class1中的任务每次返回一个空列表,因为它没有等待TaskHelper类中的InvokeTaskMagic方法的响应。
这是预期的吗?有没有办法让getSessionsTask等到TaskHelper.InvokeTaskMagic返回后再返回?
更新:以下是可工作的代码-感谢Servy的帮助。
public static class TaskHelper<T> where T : class
{
//methods
public static Task<List<T>> InvokeTaskMagic(HttpWebRequest request)
{
var resultList = new List<T>();
Task<WebResponse> task1 = Task<WebResponse>.Factory.FromAsync(
(callback, o) => ((HttpWebRequest)o).BeginGetResponse(callback, o)
, result => ((HttpWebRequest)result.AsyncState).EndGetResponse(result)
, request);
return task1.ContinueWith<List<T>>((antecedent) =>
{
if (antecedent.IsFaulted)
{
return new List<T>();
}
WebResponse webResponse;
try
{
webResponse = task1.Result;
}
catch (AggregateException ex1)
{
throw ex1.InnerException;
}
string responseString;
using (var response = (HttpWebResponse)webResponse)
{
using (Stream streamResponse = response.GetResponseStream())
{
StreamReader reader = new StreamReader(streamResponse);
responseString = reader.ReadToEnd();
reader.Close();
}
}
if (responseString != null)
{
return JsonConvert.DeserializeObject<List<T>>(responseString);
}
else
{
return new List<T>();
}
});
}
}
InvokeTaskMagic方法的调用方式如下:
var getCommentsAboutTask = Task.Factory.StartNew(() =>
{
var comments = TaskHelper<Comment>.InvokeTaskMagic(request);
return comments;
});
getCommentsAboutTask.ContinueWith((antecedent) =>
{
if (antecedent.IsFaulted)
{ return; }
var commentList = antecedent.Result.Result;
UIThread.Invoke(() =>
{
foreach (Comment c in commentList)
{
AllComments.Add(c);
GetCommentRelatedInfo(c);
}
});
});
Class2.method
指向task2
方法吗? - Soner Gönül