如何在 xamarin ios 中发布 multipartformdata？

Question

我正在使用 Xamarin IOS 为 IOS 开发移动应用程序，当我尝试使用 xamarin PostAsync() 方法将图像发布到服务器时，不幸的是它引发了异常。

public async Task<string> PostCreatePlatform(Platform new_platform, Byte[] image)
{
   new_platform.id = null;
   using (var client = new HttpClient())
   {
      client.DefaultRequestHeaders.Add("Authorization", String.Format("Token {0}", TokenInit.Token));
      var response = await client.PostAsync(b + "platforms/", new StringContent(JsonConvert.SerializeObject(new_platform, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }).ToString(),Encoding.UTF8, "application/json"));
      if (response.IsSuccessStatusCode)
      {
         if (image != null)
         {
            var TempPlatform = await response.Content.ReadAsStringAsync();
            var final = JsonConvert.DeserializeObject<Platform>(TempPlatform);
            MultipartFormDataContent form = new MultipartFormDataContent();
            new_platform.id = final.id.Value;
            form.Add(new ByteArrayContent(image, 0, image.Count()), "file");
            var response2 = await client.PostAsync(String.Format(b + "platform/{0}/attachments/upload/", new_platform.id.Value), form);
            if (response2.IsSuccessStatusCode)
            {
               return "success";
            }
         else
         {
            return "failed";
         }

         }
            return "success";
      }
      else
      {
         return "failed";
      }
 }  

InnerException: System.ObjectDisposedException

System.AggregateException: One or more errors occurred. —-> System.AggregateException: One or more errors occurred. —-> System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'System.Net.Sockets.NetworkStream'.
at System.Net.WebConnectionStream.EndWrite (System.IAsyncResult r) [0x000b2] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/System/System.Net/WebConnectionStream.cs:616
at System.IO.Stream+<>c.<BeginEndWriteAsync>b__53_1 (System.IO.Stream stream, System.IAsyncResult asyncResult) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/io/stream.cs:729
at at (wrapper delegate-invoke) System.Func`3[System.IO.Stream,System.IAsyncResult,System.Threading.Tasks.VoidTaskResult]:invoke_TResult_T1_T2 (System.IO.Stream,System.IAsyncResult)
at System.Threading.Tasks.TaskFactory`1+FromAsyncTrimPromise`1[TResult,TInstance].Complete (TInstance thisRef, System.Func`3[T1,T2,TResult] endMethod, System.IAsyncResult asyncResult, System.Boolean requiresSynchronization) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/FutureFactory.cs:1441
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable+ConfiguredTaskAwaiter.GetResult () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:447
at System.Net.Http.MultipartContent+<SerializeToStreamAsync>d__8.MoveNext () [0x00265] in <eadf07f9d3724ef0a06ee9064ef34579>:0
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable+ConfiguredTaskAwaiter.GetResult () [0x00000] in
/Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:447
at System.Net.Http.HttpClientHandler+<SendAsync>d__63.MoveNext () [0x0031d] in <eadf07f9d3724ef0a06ee9064ef34579>:0
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:535
at System.Net.Http.HttpClient+<SendAsyncWorker>d__48.MoveNext () [0x000ca] in <eadf07f9d3724ef0a06ee9064ef34579>:0
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128
at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357
at FirstApp.ApiInteracting+<PostCreatePlatform>d__7.MoveNext () [0x003e2] in /Users/team1/Downloads/testiOSbayards2-6d24bc43fee6abd445ebcaea12b76c61649468a6/FirstApp/API/ApiInteracting.cs:176
—- End of inner exception stack trace —-
at System.Threading.Tasks.Task.ThrowIfExceptional (System.Boolean includeTaskCanceledExceptions) [0x00011] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Task.cs:2157
at System.Threading.Tasks.Task`1[TResult].GetResultCore (System.Boolean waitCompletionNotification) [0x0002b] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Future.cs:562
at System.Threading.Tasks.Task`1[TResult].get_Result () [0x00000] in
/Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Future.cs:532
at FirstApp.AddPlatformTableViewController+<>c__DisplayClass247_0.<CreatePlatformButtonUpInside>b__0 () [0x00000] in /Users/team1/Downloads/testiOSbayards2-6d24bc43fee6abd445ebcaea12b76c61649468a6/FirstApp/UIClasses/AddPlatformTableViewController.cs:115
at System.Threading.Tasks.Task`1[TResult].InnerInvoke () [0x0000f] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Future.cs:680
at System.Threading.Tasks.Task.Execute () [0x00010] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Task.cs:2502
—- End of inner exception stack trace —-
at System.Threading.Tasks.Task.ThrowIfExceptional (System.Boolean includeTaskCanceledExceptions) [0x00011] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Task.cs:2157
at System.Threading.Tasks.Task`1[TResult].GetResultCore (System.Boolean waitCompletionNotification) [0x0002b] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Future.cs:562
at System.Threading.Tasks.Task`1[TResult].get_Result () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.10.0.33/src/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Future.cs:532
at FirstApp.AddPlatformTableViewController+<>c__DisplayClass247_1.<CreatePlatformButtonUpInside>b__2 () [0x00001] in /Users/team1/Downloads/testiOSbayards2-6d24bc43fee6abd445ebcaea12b76c61649468a6/FirstApp/UIClasses/AddPlatformTableViewController.cs:119
at Foundation.NSActionDispatcher.Apply () [0x00000] in /Users/builder/data/lanes/4691/3e5ac5ff/source/xamarin-macios/src/Foundation/NSAction.cs:57
at at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Users/builder/data/lanes/4691/3e5ac5ff/source/xamarin-macios/src/UIKit/UIApplication.cs:79
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/builder/data/lanes/4691/3e5ac5ff/source/xamarin-macios/src/UIKit/UIApplication.cs:63
at FirstApp.Application.Main (System.String[] args) [0x00001] in /Users/team1/Downloads/testiOSbayards2-6d24bc43fee6abd445ebcaea12b76c61649468a6/FirstApp/Main.cs:12

此外，我使用 .NET C# 编译器（不是 Mono）并使用 Web 调试工具（Fiddler）手动复制了此方法，一切正常。

更新：

问题已解决。图片尺寸太大 - 18mb。

Answer 1

试试下面的代码。这个对我有用。希望对您有所帮助。

 public class PostImageData
    {
        public int success { get; private set; }

    public async Task postData(string username, string password,string documentid, StreamContent streamContent)
    {
        UploadPhoto details = new UploadPhoto();
        try
        {
            System.Diagnostics.Debug.WriteLine("uplod done");
            var clinet = new HttpClient();
            var content = new MultipartFormDataContent();
            content.Add(streamContent, "file", "test.jpeg");
            System.Net.Http.HttpResponseMessage r =await clinet.PostAsync(YOUR_URL, content);                
            string json =await r.Content.ReadAsStringAsync();
            details = JsonConvert.DeserializeObject<UploadPhoto>(json);
            if (details.message == "Upload success")
            {
                success = 200;
            }
            success = 200;
        }
        catch (Exception e)
        {
            Debug.WriteLine(e.Message);
            success = 400;
        }
    }
    public class UploadPhoto
    {
        public string message { get; set; }
    }
}