System.InvalidOperationException: 请求提交后无法执行此操作

Question

这个问题可能已被问过多次，但他们 solution 中的 none 真的很有帮助。

我正在使用 OneSignal 向所有连接的客户端发送推送通知。我在一个服务中实现了代码并使它成为一个单例。

我想要的
我的用例是我想向用户发送通知，并立即向另一个用户发送不同的通知。

问题
它仅适用于第一个请求，之后，我不断收到此错误：

System.InvalidOperationException: This operation cannot be performed after the request has been submitted.
   at System.Net.HttpWebRequest.InternalGetRequestStream()
   at System.Net.HttpWebRequest.GetRequestStream()
   at BingoAPI.Services.NotificationService.SendNotificationAsync(Byte[] buffer) in D:\Bingo\BingoAPI\Services\NotificationService.cs:line 74

实现如下：

public NotificationService(IOptions<OneSignalNotificationSettigs> oneSignalSettings, IOptions<NotificationTemplates> notificationTemplates)
        {
            this.oneSignalSettings = oneSignalSettings;
            this.notificationTemplates = notificationTemplates;

            // request configuration
            request = WebRequest.Create(oneSignalSettings.Value.EndPoint) as HttpWebRequest;
            request.Headers.Add("authorization", oneSignalSettings.Value.Authorization);
            request.KeepAlive = true;
            request.Method = "POST";
            request.ContentType = "application/json; charset=utf-8";

        }

        private async Task SendNotificationAsync(byte[] buffer)
        {
            string responseContent = null;
            try
            {
                // here is the error
                var writer = await request.GetRequestStreamAsync();
                await writer.WriteAsync(buffer, 0, buffer.Length);
                writer.Close();

                var response = await request.GetResponseAsync() as HttpWebResponse;
                var reader = new StreamReader(response.GetResponseStream());
                responseContent = await reader.ReadToEndAsync();
            }
            catch (WebException ex)
            {
               // LOGGING
            }
        }

    }

Answer 1

据我所知，单例是指应用程序的每个后续请求都使用相同的实例。

这意味着所有两个请求都使用相同的HttpWebRequest。

因为您的 SendNotificationAsync 是异步方法。如果你同时调用这个方法两次。它将使用相同的 HttpWebRequest(request) 来发送请求。

报错告诉你第一个HttpWebRequest(request)已经提交但没有执行完成，我们无法再次提交HttpWebRequest(request)。

在我看来，您应该将服务注册为 Transient，因为我们不能重复使用 HttpWebRequest(request)。

Answer 2

我最终使用了 HttpClientFactory 而不是 HttpWebRequest，尽管我可以使它成为瞬态的。但从长远来看，这对我来说似乎不是一个解决方案运行因为每个请求都必须重新初始化很多额外的东西。而且代码更少。

public NotificationService(IOptions<OneSignalNotificationSettigs> oneSignalSettings, IOptions<NotificationTemplates> notificationTemplates,
                                   IHttpClientFactory clientFactory)
        {
            this.oneSignalSettings = oneSignalSettings;
            this.notificationTemplates = notificationTemplates;

            // request configuration
            httpClient = clientFactory.CreateClient();
            httpClient.DefaultRequestHeaders.Add("authorization", oneSignalSettings.Value.Authorization);
            request = new HttpRequestMessage(HttpMethod.Post, oneSignalSettings.Value.EndPoint);           
        }

        private async Task SerializeNotificationAsync(Object obj)
        {            
            var param = JsonConvert.SerializeObject(obj);
            var data = new StringContent(param, Encoding.UTF8, "application/json");
            await SendNotificationAsync(data);                                                
        }


        private async Task SendNotificationAsync(StringContent buffer)
        {            
            var response = await httpClient.PostAsync(request.RequestUri, buffer);

            if (!response.IsSuccessStatusCode)
            {
                // logg error

            }
        }

System.InvalidOperationException: 请求提交后无法执行此操作

System.InvalidOperationException: This operation cannot be performed after the request has been submitted

c#

asp.net

asp.net-mvc

onesignal

asp.net-core