Asynchronous 无法使Task.WaitAll正常工作
我正在尝试让Task.WaitAll工作,但我的代码从未通过WaitAll代码行。这很简单。在出现主页事件时,尝试对Web API进行两次调用。关于我做错了什么有什么建议/想法吗 下面是我的页面的OnAppearing事件中的代码Asynchronous 无法使Task.WaitAll正常工作,asynchronous,xamarin.forms,task,wait,Asynchronous,Xamarin.forms,Task,Wait,我正在尝试让Task.WaitAll工作,但我的代码从未通过WaitAll代码行。这很简单。在出现主页事件时,尝试对Web API进行两次调用。关于我做错了什么有什么建议/想法吗 下面是我的页面的OnAppearing事件中的代码 protected override void OnAppearing() { try { base.OnAppearing(); List<Task<Strin
protected override void OnAppearing()
{
try
{
base.OnAppearing();
List<Task<String>> lobj_TaskList = new List<Task<String>>();
WebAPICaller lobj_WebAPICaller = new WebAPICaller();
Debug.WriteLine("Process StartUp");
lobj_TaskList.Add(lobj_WebAPICaller.HTTPGetWebServiceAsync("/DOW/EN"));
lobj_TaskList.Add(lobj_WebAPICaller.HTTPGetWebServiceAsync("/languages/true"));
Task.WaitAll(lobj_TaskList.ToArray());
}
catch (Exception ex)
{
App.ProcessException(ex);
}
}
protected override void OnAppearing()
{
尝试
{
base.OnAppearing();
List lobj_TaskList=新列表();
WebAPICaller lobj_WebAPICaller=新的WebAPICaller();
Debug.WriteLine(“进程启动”);
lobj_TaskList.Add(lobj_WebAPICaller.httpgetwebservicecasync(“/DOW/EN”);
lobj_TaskList.Add(lobj_WebAPICaller.httpgetwebservicecasync(“/languages/true”);
Task.WaitAll(lobj_TaskList.ToArray());
}
捕获(例外情况除外)
{
App.ProcessException(ex);
}
}
这是WebAPICaller类
using System;
using System.Diagnostics;
using System.Net.Http;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace TestWebAPI
{
public class WebAPICaller : IDisposable
{
HttpClient iobj_HTTPClient = null;
public void Dispose()
{
if (iobj_HTTPClient != null)
iobj_HTTPClient.Dispose();
}
public async Task<string> HTTPGetWebServiceAsync(string ps_URI)
{
string ls_Response = "";
string ls_JSONData = "";
string ls_Prefix = "";
try
{
iobj_HTTPClient = await GetClient();
switch (Device.RuntimePlatform)
{
case Device.Android:
ls_Prefix = App.APIStandardPrefix;
break;
default:
ls_Prefix = App.APISecurePrefix;
break;
}
Debug.WriteLine("before api call");
iobj_HTTPClient.BaseAddress = new Uri(ls_Prefix);
ls_JSONData = await iobj_HTTPClient.GetStringAsync(ps_URI);
Debug.WriteLine("after api call");
ls_Response = System.Net.WebUtility.HtmlDecode(ls_JSONData);
}
catch (Exception ex)
{
Debug.WriteLine("api call error");
App.ProcessException(ex);
}
return ls_Response;
}
private async Task<HttpClient> GetClient()
{
HttpClient lobj_HTTPClient = null;
if (lobj_HTTPClient == null)
{
lobj_HTTPClient = new HttpClient();
lobj_HTTPClient.DefaultRequestHeaders.Add("Accept", "application/json");
lobj_HTTPClient.MaxResponseContentBufferSize = 2147483647;
lobj_HTTPClient.Timeout = new TimeSpan(0, 0, 0, 0, 60000);
}
return lobj_HTTPClient;
}
}
}
使用系统;
使用系统诊断;
使用System.Net.Http;
使用System.Threading.Tasks;
使用Xamarin.Forms;
命名空间TestWebAPI
{
公共类WebapCaller:IDisposable
{
HttpClient iobj_HttpClient=null;
公共空间处置()
{
if(iobj_HTTPClient!=null)
iobj_HTTPClient.Dispose();
}
公共异步任务HTTPGetWebServiceAsync(字符串ps_URI)
{
字符串ls_Response=“”;
字符串ls_JSONData=“”;
字符串ls_前缀=”;
尝试
{
iobj_HTTPClient=wait GetClient();
交换机(设备运行时平台)
{
case设备。Android:
ls_Prefix=App.apisStandardPrefix;
打破
违约:
ls_Prefix=App.apisureprefix;
打破
}
WriteLine(“在api调用之前”);
iobj_HTTPClient.BaseAddress=新Uri(ls_前缀);
ls_JSONData=wait iobj_HTTPClient.GetStringAsync(ps_URI);
WriteLine(“在api调用之后”);
ls_Response=System.Net.WebUtility.HtmlDecode(ls_JSONData);
}
捕获(例外情况除外)
{
Debug.WriteLine(“api调用错误”);
App.ProcessException(ex);
}
返回ls_响应;
}
专用异步任务GetClient()
{
HttpClient lobj_HttpClient=null;
if(lobj_HTTPClient==null)
{
lobj_HTTPClient=新的HTTPClient();
lobj_HTTPClient.DefaultRequestHeaders.Add(“Accept”、“application/json”);
lobj_HTTPClient.MaxResponseContentBufferSize=2147483647;
lobj_HTTPClient.Timeout=新的时间跨度(0,0,0,0,60000);
}
返回lobj_HTTPClient;
}
}
}
使用Task.whalll而不是Task.WaitAll
Wheall将等待所有任务完成。等待链将在第一个异常时中止等待,但继续执行未等待的任务。这会导致意外的并发
看看下面的代码,它将帮助你
protected async override void OnAppearing()
{
try
{
base.OnAppearing();
List<Task<String>> lobj_TaskList = new List<Task<String>>();
WebAPICaller lobj_WebAPICaller = new WebAPICaller();
Debug.WriteLine("Process StartUp");
lobj_TaskList.Add(lobj_WebAPICaller.HTTPGetWebServiceAsync("/DOW/EN"));
lobj_TaskList.Add(lobj_WebAPICaller.HTTPGetWebServiceAsync("/languages/true"));
await Task.WhenAll(lobj_TaskList.ToArray());
}
catch (Exception ex)
{
App.ProcessException(ex);
}
}
protected async override void OnAppearing()
{
尝试
{
base.OnAppearing();
List lobj_TaskList=新列表();
WebAPICaller lobj_WebAPICaller=新的WebAPICaller();
Debug.WriteLine(“进程启动”);
lobj_TaskList.Add(lobj_WebAPICaller.httpgetwebservicecasync(“/DOW/EN”);
lobj_TaskList.Add(lobj_WebAPICaller.httpgetwebservicecasync(“/languages/true”);
wait Task.WhenAll(lobj_TaskList.ToArray());
}
捕获(例外情况除外)
{
App.ProcessException(ex);
}
}
这似乎允许代码在所有任务完成之前继续。我想等到它们全部完成。它是在等待所有任务完成。在任务之前添加等待。Wheall工作。谢谢