与PostAsync方法HttpClient的错误

本文介绍了与PostAsync方法HttpClient的错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

使得使用HttpClient的一个第三方API PostAsync电话时。当我做client.PostAsync我正是看到了这个错误。任何想法可能已经造成的？

code：

公共类JobController：AsyncController{    公众的ActionResult的ViewPage（）    {        返回视图（〜/查看/页/ Submit.cshtml）;    }    私人常量字符串的serviceUrl =htt​​ps://api.3points.io/v1/applications/;    [HttpPost]    公共异步任务＆LT;＆的ActionResult GT;提交（）    {        VAR的客户=新的HttpClient（）;        VAR FORMDATA =新MultipartFormDataContent（）;        变种EN codeD = Convert.ToBase64String（Encoding.UTF8.GetBytes（ABC123））;        client.DefaultRequestHeaders.Authorization =新AuthenticationHeaderValue（基本，恩codeD）;        的foreach（在Request.Form.AllKeys VAR键）            formData.Add（新的StringContent（的Request.Form [关键]）的String.Format（\\{0} \\，键））;        的foreach（在Request.Files.AllKeys字符串键）        {            var文件= Request.Files [关键]            如果（文件== NULL || file.ContentLength＆LT; = 0）继续;            HttpContent FILESTREAM =新StreamContent（file.InputStream）;            formData.Add（FILESTREAM，钥匙，file.FileName）;        }        VAR响应=等待client.PostAsync（serviceURL中，FORMDATA）;        VAR成功=真;        如果（response.IsSuccessStatus code！）成功=FALSE;        返回新JsonResult {数据=成功};    }}

错误：

System.NullReferenceException了未处理的HResult = -2147467261消息=对象引用未设置到对象的实例。来源=的System.Web堆栈跟踪：   在System.Web.ThreadContext.AssociateWithCurrentThread（布尔setImpersonationContext）   在System.Web.HttpApplication.OnThreadEnterPrivate（布尔setImpersonationContext）   在System.Web.LegacyAspNetSynchronizationContext.CallCallbackPossiblyUnderLock（SendOrPostCallback回调，对象状态）   在System.Web.LegacyAspNetSynchronizationContext.CallCallback（SendOrPostCallback回调，对象状态）   在System.Threading.Tasks.AwaitTaskContinuation.RunCallback（ContextCallback回调，对象状态，任务和放大器; currentTask）---从previous位置堆栈跟踪，其中引发异常的结尾---   在System.Threading.Tasks.AwaitTaskContinuation＆LT; ThrowAsyncIfNecessary＆GT; b__1（一个Object）   在System.Threading.ExecutionContext.RunInternal（ExecutionContext中的ExecutionContext，ContextCallback回调，对象状态，布尔preserveSyncCtx）   在System.Threading.ExecutionContext.Run（ExecutionContext中的ExecutionContext，ContextCallback回调，对象状态，布尔preserveSyncCtx）   在System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem（）   在System.Threading.ThreadPoolWorkQueue.Dispatch（）

解决方案

我会改变

VAR响应= client.PostAsync（serviceURL中，FORMDATA）。结果

到

VAR响应=等待client.PostAsync（serviceURL中，FORMDATA）;

和然后监视后的错误。

When making PostAsync call using HttpClient to a 3rd party API. I am seeing this error exactly when I do client.PostAsync. Any idea what could have been causing this?

Code:

public class JobController : AsyncController { public ActionResult ViewPage() { return View("~/Views/Pages/Submit.cshtml"); } private const string ServiceUrl = "api.3points.io/v1/applications/"; [HttpPost] public async Task<ActionResult> Submit() { var client = new HttpClient(); var formData = new MultipartFormDataContent(); var encoded = Convert.ToBase64String(Encoding.UTF8.GetBytes("abc123")); client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", encoded); foreach (var key in Request.Form.AllKeys) formData.Add(new StringContent(Request.Form[key]), String.Format("\"{0}\"", key)); foreach (string key in Request.Files.AllKeys) { var file = Request.Files[key]; if (file == null || file.ContentLength <= 0) continue; HttpContent fileStream = new StreamContent(file.InputStream); formData.Add(fileStream, key, file.FileName); } var response = await client.PostAsync(ServiceUrl, formData); var success = "True"; if (!response.IsSuccessStatusCode) success = "False"; return new JsonResult { Data = success }; } }

Error:

System.NullReferenceException was unhandled HResult=-2147467261 Message=Object reference not set to an instance of an object. Source=System.Web StackTrace: at System.Web.ThreadContext.AssociateWithCurrentThread(Boolean setImpersonationContext) at System.Web.HttpApplication.OnThreadEnterPrivate(Boolean setImpersonationContext) at System.Web.LegacyAspNetSynchronizationContext.CallCallbackPossiblyUnderLock(SendOrPostCallback callback, Object state) at System.Web.LegacyAspNetSynchronizationContext.CallCallback(SendOrPostCallback callback, Object state) at System.Threading.Tasks.AwaitTaskContinuation.RunCallback(ContextCallback callback, Object state, Task& currentTask) --- End of stack trace from previous location where exception was thrown --- at System.Threading.Tasks.AwaitTaskContinuation.<ThrowAsyncIfNecessary>b__1(Object s) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() at System.Threading.ThreadPoolWorkQueue.Dispatch()

解决方案

I would change

var response = client.PostAsync(ServiceUrl, formData).Result

to

var response = await client.PostAsync(ServiceUrl, formData);

And then monitor for errors after that.