该请求需要缓冲数据以成功HttpClient

Question

我尝试使用POST方法

将字典内容发送到服务器

public async Task<T> postConnection(string GETParam, Dictionary<string, string> values, bool isRegistration = false)
{
    HttpResponseMessage response;
    string responseString;
    try
    { 
        using (var client = new HttpClient() { MaxResponseContentBufferSize = 256000 }) 
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", tocken);
            var content = new FormUrlEncodedContent(values);
            response = await client.PostAsync(url, content);
            responseString = await response.Content.ReadAsStringAsync();
        }
    }

但是当我运行代码时，它会给我错误 WebException: The request requires buffering data to succeed HttpClient。

我不想使用WebRequest或WebClient发出请求，我只想使用HttpClient。

尝试发送head request时，question已经存在但发生相同异常的情况说明问题仅发生在Xamarin个项目上，但问题未得到解答然而。刚刚提到他使用WebRequest来解决问题。

Xamarin.Forms上此代码的错误是什么？如何使用HttpClient来解决？

修改

完全例外

{System.Net.WebException: The request requires buffering data to succeed.
  at System.Net.HttpWebRequest.EndGetResponse (IAsyncResult asyncResult) [0x0005e] in /Users/builder/data/lanes/3540/1cf254db/source/mono/mcs/class/System/System.Net/HttpWebRequest.cs:1005 
  at System.Threading.Tasks.TaskFactory`1[TResult].FromAsyncCoreLogic (IAsyncResult iar, System.Func`2 endFunction, System.Action`1 endAction, System.Threading.Tasks.Task`1 promise, Boolean requiresSynchronization) [0x00014] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/threading/Tasks/FutureFactory.cs:550 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00047] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:535 
  at System.Net.Http.HttpClientHandler+<SendAsync>c__async0.MoveNext () [0x003d6] in /Users/builder/data/lanes/3540/1cf254db/source/mono/mcs/class/System.Net.Http/System.Net.Http/HttpClientHandler.cs:372 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00047] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:535 
  at System.Net.Http.HttpClient+<SendAsyncWorker>c__async0.MoveNext () [0x000a9] in /Users/builder/data/lanes/3540/1cf254db/source/mono/mcs/class/System.Net.Http/System.Net.Http/HttpClient.cs:276 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00047] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 
  at HuraApp.API.Connection`1+<postConnection>d__1[T].MoveNext () [0x0011c] in C:\Users\Nullsky\documents\visual studio 2015\Projects\HuraApp\HuraApp\HuraApp\API\Connection.cs:43 }

Answer 1

基于HttpWebRequest的Mono源代码，看起来服务器正在发出重定向，并且HttpWebRequest（由HttpClient负责使用）不处理它。

我不确定使用的是什么版本的Mono源，但这似乎是一个可能的候选者： https://github.com/mono/mono/blob/cc3f4c60379c3839dd4259e171bb4539d21f2157/mcs/class/System/System.Net/HttpWebRequest.cs

该版本有＆＃34; throw＆＃34;在HttpWebRequest.EndGetResponse的第1005行，它匹配您正在查看的异常堆栈。异常中的字符串，＆＃34;请求需要缓冲数据才能成功＆＃34;来自HttpWebRequest.Redirect。

下一步是使用Fiddler（或类似的）来复制Xamarin客户端试图查看从服务器获得的响应的确切POST消息。

Answer 2

不幸的是

var response = await client.PostAsyn(url, content);

在完成之前下载整个响应，因此它不使用任何缓冲。唯一的选择是使用，

var request = new HttpMessageRequest(url);
request.Content = content;
var response = await client.SendAsync(request, 
      HttpCompletionOption.ResponseHeadersRead);

下载标题后，

HttpCompletionOption.ResponseHeadersRead选项会使HttpClient从SendAsync返回。你可以等待阅读内容。

Answer 3

对于您在提出头部请求时链接的相同问题，请参阅以下链接，其中xamarin论坛中提供了其中一个解决方案，他们在向Google网址发出POST请求（200）时遇到了同样的问题。

这种情况下的解决方案是将URL更改为实际页面而不是重定向。

这里是链接Solution for the issue

希望它有所帮助。

Answer 4

这是在iOS和/或Android上发生的吗？

我会尝试将HttpClient处理程序更改为本机处理程序。这解决了许多问题，包括很多主题（TLS是一个很大的问题）。对于iOS，使用NSUrlSession处理程序，对于Android，请尝试使用AndroidClientHandler。您应该可以使用HttpClient来处理Xamarin的所有内容。