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I am upgrading a Xamarin app to MAUI and thought of decoupling things a bit. Before i had a datastore which handled all requests to an API, now i have a service for each section of the app from which requests go to a HttpManager, problem is when the policy retries, it works for the first time but on the second retry it fails with the message "Cannot access a closed Stream". Searched a bit but couldn't find a fix.

I call the service from the viewModel.

LoginViewModel.cs

readonly IAuthService _authService; public LoginViewModel(IAuthService authService) { _authService = authService; } [RelayCommand] private async Task Login() { ... var loginResponse = await _authService.Login( new LoginDTO(QRSettings.StaffCode, Password, QRSettings.Token)); ... }

In the service i set send the data to the HttpManager and process the response

AuthService.cs

private readonly IHttpManager _httpManager; public AuthService(IHttpManager manager) { _httpManager = manager; } public async Task<ServiceResponse<string>> Login(LoginDTO model) { var json = JsonConvert.SerializeObject(model); var content = new StringContent(json, Encoding.UTF8, "application/json"); var response = await _httpManager.PostAsync<string>("Auth/Login", content); ... }

And in here i send the request.

HttpManager.cs

readonly IConnectivity _connectivity; readonly AsyncPolicyWrap _retryPolicy = Policy .Handle<TimeoutRejectedException>() .WaitAndRetryAsync(3, _ => TimeSpan.FromSeconds(1), (exception, timespan, retryAttempt, context) => { App.AppViewModel.RetryTextVisible = true; App.AppViewModel.RetryText = $"Attempt number {retryAttempt}..."; }) .WrapAsync(Policy.TimeoutAsync(11, TimeoutStrategy.Pessimistic)); HttpClient HttpClient; public HttpManager(IConnectivity connectivity) { _connectivity = connectivity; HttpClient = new HttpClient(); } public async Task<ServiceResponse<T>> PostAsync<T>(string endpoint, HttpContent content, bool shouldRetry = true) { ... // Post request var response = await Post($""http://10.0.2.2:5122/{endpoint}", content, shouldRetry); ... } async Task<HttpResponseMessage> Post(string url, HttpContent content, bool shouldRetry) { if (shouldRetry) { // This is where the error occurs, in the PostAsync var response = await _retryPolicy.ExecuteAndCaptureAsync(async token => await HttpClient.PostAsync(url, content, token), CancellationToken.None); ... } ... }

And this is the MauiProgram if it matters

... private static MauiAppBuilder RegisterServices(this MauiAppBuilder builder) { ... builder.Services.AddSingleton<IHttpManager, HttpManager>(); builder.Services.AddSingleton<IAuthService, AuthService>(); return builder; }

Can't figure out what the issue is... I tried various try/catches, tried finding a solution online but no luck. On the second retry it always gives that error

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  • Your HttpContent can not be reused out of the box if it is a stream. You need to rewind the underlying stream before re-issuing an http request. Commented Dec 14, 2022 at 15:15
  • what do you mean by rewinding it ? Commented Dec 14, 2022 at 15:29
  • see this stackoverflow.com/questions/26942514/… Commented Dec 14, 2022 at 15:31
  • Setting the stream's Position from the last to the first to be able to re-read its content Commented Dec 14, 2022 at 15:54

2 Answers 2

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Disclaimer: In the comments section I've suggested to rewind the underlying stream. That suggestion was wrong, let me correct myself.

TL;DR: You can't reuse a HttpContent object you need to re-create it.

In order to be able to perform a retry attempt with a POST verb you need to recreate the HttpContent payload for each attempt.

There are several ways to fix your code:

Pass the serialized string as parameter

async Task<HttpResponseMessage> Post(string url, string content, bool shouldRetry) { if (shouldRetry) { var response = await _retryPolicy.ExecuteAndCaptureAsync(async token => await HttpClient.PostAsync(url, new StringContent(content, Encoding.UTF8, "application/json"), token), CancellationToken.None); ... } ... }

Pass the to-be-serialized object as parameter

async Task<HttpResponseMessage> Post(string url, object content, bool shouldRetry) { if (shouldRetry) { var response = await _retryPolicy.ExecuteAndCaptureAsync(async token => await HttpClient.PostAsync(url, JsonContent.Create(content), token), CancellationToken.None); ... } ... }
  • Here we are taking advantage of the JsonContent type which was introduced in .NET 5

Pass the to-be-serialized object as parameter #2

async Task<HttpResponseMessage> Post(string url, object content, bool shouldRetry) { if (shouldRetry) { var response = await _retryPolicy.ExecuteAndCaptureAsync(async token => await HttpClient.PostAsJsonAsync(url, content, token), CancellationToken.None); ... } ... }
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13 Comments

Coming back to this after a while, in the end i went with this var response = await _retryPolicy.ExecuteAndCaptureAsync(async token => await HttpClient.PostAsync(url, new StringContent(json, Encoding.UTF8, "application/json"), token), CancellationToken.None); and it has worked while using the local API on IIS but as soon as i connect to an API on a live server i get the cannot access a closed stream error again. Any ideas why ? :)
@AdrianRadulescu Could you please share with me the related code fragment via pastebin.com?
sure, pastebin.com/R3cERYqB, the other parts of the code are mainly the same, the only difference is that the class is static now, form which i control the requests sent from the app
@AdrianRadulescu How do you get the HttpClient instance?
@AdrianRadulescu I've checked it and I don't see any reason why do you have the observed behaviour. It seems like you recreate the disposables rather than reusing them (which is good), so I'm out of ideas. Sorry :(
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I am merely putting this out there because I ran across this stream closed error when I was doing web service calls with post in maui against a web service that I have written in azure. I'm converting some old code from xamarin to maui. I pulled my hair out for a couple of hours. then I looked at the server name and protocol I was using. I had inadvertently used http as the protocol. I switched to using https and all of the errors went away.

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