与PostAsync方法HttpClient的错误 [英] HttpClient error with PostAsync method

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 = "https://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.

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