c# - HttpClient PostAsync() 不起作用

Question

在我的 Xamarin 表单应用程序中

我正在尝试将 Json 字符串发布到我的网络服务，即 RestFul API
当我使用以下代码时:

public static async Task<bool> SaveRolAsync(Methods Method, Role Rol)
    {
        try
        {
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            var uri = ("http://myservice.com/roles/");
            HttpResponseMessage response = null;

            try
            {
                var jSettings = new JsonSerializerSettings();
                jSettings.NullValueHandling = NullValueHandling.Ignore;
                jSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

                var JsonData = JsonConvert.SerializeObject(Rol);
                var RoleContent = new StringContent(JsonData, Encoding.UTF8, "application/json");

                if (Method == Methods.PUT || Method == Methods.PATCH)
                {
                    response = await client.PutAsync(uri, RoleContent);
                }

                if (Method == Methods.POST)
                {
                    response = await client.PostAsync(uri, RoleContent);
                }

                if (Method == Methods.DELETE)
                {
                    throw new NotImplementedException();
                }

                return response.IsSuccessStatusCode;

            }
            catch (JsonException jse)
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            // Exceptions Throws here
            // @T This line i got The request requires buffering data to succeed
            return false;
        }
    }

异常抛出:

The request requires buffering data to succeed

堆栈跟踪:

{System.Net.WebException: The request requires buffering data to succeed. at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) [0x00064] in :0 at System.Threading.Tasks.TaskFactory1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func2[T,TResult] endFunction, System.Action1[T] endAction, System.Threading.Tasks.Task1[TResult] promise, System.Boolean requiresSynchronization) [0x00014] in :0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in :0 at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Net.Http.HttpClientHandler+<SendAsync>c__async0.MoveNext () [0x0041e] in <566d6cf6576345098cb5e08ad43d5e78>:0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in :0 at System.Net.Http.HttpClient+c__async0.MoveNext () [0x000f3] in <566d6cf6576345098cb5e08ad43d5e78>:0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in :0 at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in :0 at MyAPP.Webservice+d__4.MoveNext () [0x000d0] in C:\MyProject\Classes\Webservice.cs:140 }

**还尝试过:SendAsync() Ty M. Wiśnicki **

public static async Task<bool> SaveRolAsync(MediwareLib.Methods Method, Role Rol)
    {
        try
        {
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            var uri = (BaseRequestUrl + "roles/");
            HttpResponseMessage response = null;
            var request = new HttpRequestMessage();

            try
            {
                var jSettings = new JsonSerializerSettings();
                jSettings.NullValueHandling = NullValueHandling.Ignore;
                jSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

                var JsonData = JsonConvert.SerializeObject(Rol);

                var RoleContent = new StringContent(JsonData, Encoding.UTF8, "application/json");

                if (Method == MediwareLib.Methods.PUT || Method == MediwareLib.Methods.PATCH)
                {
                    request = new HttpRequestMessage(HttpMethod.Put, uri);
                    request.Content = RoleContent;

                    response = await client.SendAsync(request,
                    HttpCompletionOption.ResponseHeadersRead);
                }

                if (Method == MediwareLib.Methods.POST)
                {
                    request = new HttpRequestMessage(HttpMethod.Post, uri);
                    request.Content = RoleContent;

                    response = await client.SendAsync(request,
                    HttpCompletionOption.ResponseHeadersRead);
                }

                if (Method == MediwareLib.Methods.DELETE)
                {
                    throw new NotImplementedException();
                    // response = await client.DeleteAsync(uri + Rol.Id);
                }

                return response.IsSuccessStatusCode;

            }
            catch (JsonException jse)
            {
                Globals.Log("SaveRolAsync: " + jse.ToString());
                return false;
            }
        }
        catch (Exception ex)
        {
            Globals.Log("SaveRolAsync: " + ex.ToString());
            return false;
        }

    }

Answer 1

由于您使用的是 .Result或 .Wait或 await这最终会导致 僵局在你的代码中。

您可以使用 ConfigureAwait(false)在 async 的方法防止死锁

像这样:

response = await client.PostAsync(uri, RoleContent).ConfigureAwait(false);

you can use ConfigureAwait(false) wherever possible for Don't Block Async Code .