MonoでHttpClientがエラーをスローする

Question

MonoでHttpClientを使用しようとしています（.NET Frameworkでは正常に動作します）がエラーになります。

04-25 14:07:14.952 I/Choreographer(3238): Skipped 144 frames! The application may be doing too much work on its main thread. 
[0:] An error occurred while sending the request 
[0:] at System.Net.Http.HttpClientHandler+<SendAsync>c__async0.MoveNext() [0x0047a] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/System.Net.Http/System.Net.Http/HttpClientHandler.cs:383 
--- End of stack trace from previous location where exception was thrown --- 
    at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() [0x0000c] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/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/4468/f913a78a/source/mono/mcs/class/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/4468/f913a78a/source/mono/mcs/class/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/4468/f913a78a/source/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
    at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult() [0x00000] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:535 
    at System.Net.Http.HttpClient+<SendAsyncWorker>c__async0.MoveNext() [0x000a9] in /Users/builder/data/lanes/4468/f913a78a/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/4468/f913a78a/source/mono/mcs/class/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/4468/f913a78a/source/mono/mcs/class/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/4468/f913a78a/source/mono/mcs/class/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/4468/f913a78a/source/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
    at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult() [0x00000] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 
    at MyWebClient+<MakeRequest>d__63.MoveNext() [0x0019b] in <4eeea402c92c428f818fd28bf1ed35bc>:0 

マイコード;

var httpClient = new HttpClient { Timeout = new TimeSpan(0, 0, (int) TimeOut) }; 
foreach (var header in Headers) 
{ 
    httpClient.DefaultRequestHeaders.Add(header.Key, header.Value); 
} 

// attempting to workaround Xamarin bug 
// http://forums.xamarin.com/discussion/17770/length-required-error-in-http-post-since-latest-release 
var requestcontent = new HttpRequestMessage(HttpMethod.Post, Url) 
{ 
    Content = !string.IsNullOrEmpty(RequestStr) 
     ? new StringContent(RequestStr, Encoding.UTF8, "application/json") 
     : new ByteArrayContent(new byte[0]) 
}; 

using (HttpResponseMessage response = await httpClient.SendAsync(requestcontent)) 
{ 
    using (HttpContent content = response.Content) 
    { 
     ResponseStr = await content.ReadAsStringAsync(); 
    } 
} 

私は（ここではHttpClientHandler.cs:383詳細な）問題を回避してコードを試みたが、それはまだエラーがスローされますが、NET標準& NET46の下で完璧に動作します。

ここではXamarinパッケージのバージョンです。

Xamarin.Android.Support.Animated.Vector.Drawable.23.3.0 
Xamarin.Android.Support.Design.23.3.0 
Xamarin.Android.Support.v4.23.3.0 
Xamarin.Android.Support.v7.AppCompat.23.3.0 
Xamarin.Android.Support.v7.CardView.23.3.0 
Xamarin.Android.Support.v7.MediaRouter.23.3.0 
Xamarin.Android.Support.v7.RecyclerView.23.3.0 
Xamarin.Android.Support.Vector.Drawable.23.3.0 
Xamarin.Forms.2.3.4.231 

Answer 1

アプリケーションはそのメインスレッド上であまりにも多くの仕事をやっていてもよいです。

これは、通常、メインUIスレッドでHTTP要求を実行しようとすると発生します。