我需要使用相同的HttpClient实例从不同方法执行4个HttpClient请求，我认为这会导致线程安全问题。让我再解释一下。
在我开发的Windows Phone应用程序中，有一个“MainViewModel”＆＃39;类。此类具有异步方法，以从Web服务器获取数据并处理响应。 Async方法名为＆＃39; LoadData＆＃39;。我在这个类中甚至还有两个Async方法（＆＃39; ScheduleArrayAsync＆＃39;和＃39; CurrActivityAsync＆＃39;）来帮助处理我从服务器获取的数据。
来自＆＃39; LoadData＆＃39;方法我做3个HttpClient请求（这部分工作就像魅力），在处理来自所有这三个请求的响应时，我需要调用＆＃39; ScheduleArrayAsync＆＃39;方法。从那里我必须创建一个新的HttpClient请求（这是问题所在）。即使我使用try / catch语句，也不会生成最后一个请求，也不会生成错误代码。
是什么让我认为它是一个线程问题，如果我将最后一个HttpClient请求移动到＆＃39; LoadData＆＃39;方法，就像测试一样，它再次起作用。
MainViewModel类： -
public class MainViewModel : INotifyPropertyChanged
{
public MainViewModel()
{
this.Employees = new ObservableCollection<Employee>();
}
public ObservableCollection<Employee> Employees { get; private set; }
private JsonTextWriter jsonW;
private string Owner;
private RequestResponse reqPList;
public bool IsDataLoaded
{
get;
private set;
}
public async void LoadData()
{
var baseUri = new Uri("https://uri/");
await CookieHandler.GetCookies(baseUri); // A separate request to get some cookies
reqPList = new RequestResponse(); // The class that handle the Httpclinet
await reqPList.GetResponse(baseUri, pList); // First request
XmlConvertor.ConvertToXml(reqPList.Response);
var phoneListResponse = XmlConvertor.XmlString;
await reqPList.GetResponse(baseUri, currActiv); // Second request
XmlConvertor.ConvertToXml(reqPList.Response);
var currActivResponse = XmlConvertor.XmlString;
await reqPList.GetResponse(baseUri, sched); // Third request
XmlConvertor.ConvertToXml(reqPList.Response);
var schedResponse = XmlConvertor.XmlString;
//await reqPList.GetSlotInforPOST("154215");
var handler = new DataHandler();
await handler.phoneListHandler(phoneListResponse);
await handler.CurrActivitiesHandler(currActivResponse);
await handler.ScheduleHandler(schedResponse);
/// Do some processing included call this line
#region Current activity
CurrActivityAsync(item, handler.currActivitiesJSON);
#endregion
this.IsDataLoaded = true;
}
private async void CurrActivityAsync(JToken token, string jString)
{
// Some processing
}
private async void ScheduleArrayAsync(JToken token, string jString)
{
try
{
// Do some more processing and call the fourth request
if (addedInfo[0].Contains("slotInfo"))
await reqPList.GetSlotInforPOST(addedInfo[1]);
else if (addedInfo[0].Contains("vacationInfo"))
await reqPList.GetVacationSlotInfoPOST(addedInfo[1], addedInfo[2]);
}
catch (Exception exp)
{
var d = exp.Message;
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
以下是RequestResponse类： -
public class RequestResponse
{
public string Response { get; private set; }
private HttpClient client = new HttpClient(new HttpClientHandler()
{
UseCookies = true,
CookieContainer = CookieHandler.Cookiejar,
AllowAutoRedirect = false,
AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip
});
public async Task<string> GetResponse(Uri baseuri, string uriString)
{
if (client.BaseAddress == null)
{
client.BaseAddress = baseuri;
}
client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/xhtml+xml"));
var response = await client.GetAsync(baseuri + uriString);
string webresponse = null;
if (response.IsSuccessStatusCode)
{
var resp = await response.Content.ReadAsByteArrayAsync();
var encode = Encoding.GetEncoding("iso-8859-1");
var respString = encode.GetString(resp, 0, resp.Length - 1);
webresponse = respString;
}
return Response = webresponse;
}
public async Task<string> GetSlotInforPOST(string timeId)
{
/// If the method is called from inside 'LoadData' it works.
/// But if it is called from inside ScheduleArrayAsync, it will break at line marked with //***
try
{
var baseUri = new Uri("https://uri/");
const string slotInfo = "cgi-bin/slotInfo.pl";
if (client.BaseAddress == null)
client.BaseAddress = baseUri;
client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded"));
HttpContent content = new FormUrlEncodedContent(new[]
{
new KeyValuePair<string,string>("timeId",timeId)
});
var response = await client.GetAsync(baseUri + slotInfo); // ***
string webresponse;
if (response.IsSuccessStatusCode)
{
var respo = await client.PostAsync(baseUri + slotInfo, content);
var resp = await respo.Content.ReadAsByteArrayAsync();
var encode = Encoding.GetEncoding("iso-8859-1");
var respString = encode.GetString(resp, 0, resp.Length - 1);
webresponse = respString;
}
}
catch (Exception exp)
{
var s = exp.Message;
}
return Response;
}
public async Task<string> GetVacationSlotInfoPOST(string vacationId, string date)
{
// Do some HttpClient Request
}
}
我理解这个问题吗？如何克服它？因为我真的需要从＆＃39; ScheduleArrayAsync＆＃39;制作最后一个HttpClient请求。而不是来自＆＃39; LoadData＆＃39;
修改 只是想提一下，在我努力解决问题的过程中，我在RequestResponse类中的每个方法中都有不同的HttpClient实例。除了我上面提到的，当我从内部调用第四个请求时，LoadData＆＃39;方法即使它是httpclient的一个实例，一切都按预期工作。
答案 0 :(得分：2)
在某些方法中，您可能会将async void作为签名。使用async void将阻止调用函数捕获抛出异常。异步void方法抛出的异常只能被全局异常处理程序捕获。
答案 1 :(得分：0)
最后我已经修好了，多亏了Darrel。
要解决问题，我需要更改＆＃39; CurrActivityAsync＆＃39;方法
这
private async void CurrActivityAsync(JToken token, string jString)
到
private void CurrActivityAsync(JToken token, string jString)
由于这种方法没有等待它内部，这就是为什么它不需要签名中的异步。我的坏事我在原帖中没有提到过。
这是我唯一需要做的事情，但我甚至改变了我的＆＃39; ScheduleArrayAsync＆＃39; 更准确的是Async。
这
private async void ScheduleArrayAsync(JToken token, string jString)
到
private async Task ScheduleArrayAsync(JToken token, string jString)
Darrel 请您写下您的最后一条评论作为答案，以便获得一些学分。