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Getting "Response status code does not indicate success: 502 (Bad Gateway)" from Asp.net Core MVC Web App hosted in Azure

I have a client application built on Asp.net core MVC (V 1.1.1) and a Web API built on Asp.net core (v 2.1). I had hosted both on Azure.
While making some requests, the web app is failing and giving 502 Bad Gateway response.
Response status code does not indicate success: 502 (Bad Gateway).
The specified CGI application encountered an error and the server terminated the process.
This issue is intermittent, however, seems happening when request is taking more than 2 min to process. I have set up requestTimeout to 20 min on both client and API side in Web.config file still didn't get it resolved. Sometimes, the same request is being processed in less time and I am getting response.
Additionally, the 5 min timeout for Httpclient has also been set but no luck.
<aspNetCore requestTimeout="00:20:00"/>
_httpClient.Timeout = new TimeSpan(0, 5, 0);
I have tested the app locally and can't face this issue, also able to get response even it take more than 3 min to process.
It seems that Azure web app is not waiting for request to get processed if it's crossing 2 min. However, the azure session timeout specifies 230 seconds (3.8 min) but still it's not waiting and the app is not considering this case as an error and not logging anything.
Client Side code:
public class ApiClientFactory
{
private static Uri ApiUrl;
private static Lazy<ApiClient> restClient = new Lazy<ApiClient>(
() => new ApiClient(ApiUrl),
LazyThreadSafetyMode.ExecutionAndPublication);
static ApiClientFactory()
{
ApiUrl = new Uri(Convert.ToString(ConfigurationManager.AppSettings["WebAPIUrl"]));
}
public static ApiClient Instance
{
get
{
return restClient.Value;
}
}
}
public class ApiClient
{
private readonly HttpClient _httpClient;
private readonly Uri BaseEndPointUrl;
public ApiClient(Uri baseEndPointUrl)
{
if (baseEndPointUrl == null)
throw new ArgumentNullException("baseEndPointUrl");
BaseEndPointUrl = baseEndPointUrl;
_httpClient = new HttpClient();
_httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
_httpClient.Timeout = new TimeSpan(0, 5, 0); //Timeout needed for few modules to get results from db.
}
private HttpContent CreateHttpContent<T>(T content)
{
var json = JsonConvert.SerializeObject(content, MicrosoftDateFormatSettings);
return new StringContent(json, Encoding.UTF8, "application/json");
}
private static JsonSerializerSettings MicrosoftDateFormatSettings
{
get
{
return new JsonSerializerSettings
{
DateFormatHandling = DateFormatHandling.MicrosoftDateFormat
};
}
}
public async Task<T1> PostAsync<T1, T2>(string url, T2 content, string token)
{
try
{
_httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var response = await _httpClient.PostAsync(url, CreateHttpContent<T2>(content));
if (response.StatusCode == HttpStatusCode.InternalServerError){
var exception = await response.Content.ReadAsStringAsync();
throw new Exception(exception);
}
response.EnsureSuccessStatusCode();
var data = await response.Content.ReadAsStringAsync();
return JsonConvert.DeserializeObject<T1>(data);
}
catch (Exception ex){throw ex;}
}
}
Please assist where it's having an issue.

You can implement a method that retry your requests, or simply use .Net Polly for this kind of errors. Is not a good practice to increase your timeout setup.
Method:
private async Task<bool> PostAsync()//Params you need
{
HttpStatusCode[] httpStatusCodesWorthRetrying =
{
HttpStatusCode.RequestTimeout,
HttpStatusCode.InternalServerError,
HttpStatusCode.BadGateway,
HttpStatusCode.ServiceUnavailable,
HttpStatusCode.GatewayTimeout
};
var maxAttempts = 0;
while (maxAttempts < 3)
{
var response = await _httpClient.PostAsync(requestUrl, CreateHttpContent<T2>(content));
if (!httpStatusCodesWorthRetrying.Contains(response.StatusCode))
{
return true;
}
maxAttempts ++;
await Task.Delay(300);
}
return false;
}
Polly:
private async Task PostAsync()//Params you need
{
HttpStatusCode[] httpStatusCodesWorthRetrying =
{
HttpStatusCode.RequestTimeout,
HttpStatusCode.InternalServerError,
HttpStatusCode.BadGateway,
HttpStatusCode.ServiceUnavailable,
HttpStatusCode.GatewayTimeout
};
_retryPolicy = Policy
.Handle<HttpRequestException>()
.OrResult<HttpResponseMessage>(r => httpStatusCodesWorthRetrying.Contains(r.StatusCode))
.WaitAndRetry(4, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));
_retryPolicy.Execute(await _httpClient.PostAsync(requestUrl, CreateHttpContent<T2>(content)));
}

We thought that the following could be the possible reasons.
At the time of testing, Network related issue between two hosted applications while processing the given
request and to deliver the response. Before the API delivers the response the Web app
might be timing out.
Made the following code change in the API client class. (it's posted in the question).I am not certain about the subtle difference between awaiting the task and getting the Result from the task. But after this change we no longer experienced the issue, additionally did some load testing also but still didn't face that later on.
From
var response = await _httpClient.PostAsync(requestUrl, CreateHttpContent<T2>(content));
To
var response = _httpClient.PostAsync(requestUrl, CreateHttpContent<T2>(content)).Result;
Note: Enabling the Analytics options for the hosted domains in Azure would give us good insights to narrow down this type of issues.

Creating a proxy to another web api with Asp.net core

I'm developing an ASP.Net Core web application where I need to create a kind of "authentication proxy" to another (external) web service.
What I mean by authentication proxy is that I will receive requests through a specific path of my web app and will have to check the headers of those requests for an authentication token that I'll have issued earlier, and then redirect all the requests with the same request string / content to an external web API which my app will authenticate with through HTTP Basic auth.
Here's the whole process in pseudo-code
Client requests a token by making a POST to a unique URL that I sent him earlier
My app sends him a unique token in response to this POST
Client makes a GET request to a specific URL of my app, say /extapi and adds the auth-token in the HTTP header
My app gets the request, checks that the auth-token is present and valid
My app does the same request to the external web API and authenticates the request using BASIC authentication
My app receives the result from the request and sends it back to the client
Here's what I have for now. It seems to be working fine, but I'm wondering if it's really the way this should be done or if there isn't a more elegant or better solution to this? Could that solution create issues in the long run for scaling the application?
[HttpGet]
public async Task GetStatement()
{
//TODO check for token presence and reject if issue
var queryString = Request.QueryString;
var response = await _httpClient.GetAsync(queryString.Value);
var content = await response.Content.ReadAsStringAsync();
Response.StatusCode = (int)response.StatusCode;
Response.ContentType = response.Content.Headers.ContentType.ToString();
Response.ContentLength = response.Content.Headers.ContentLength;
await Response.WriteAsync(content);
}
[HttpPost]
public async Task PostStatement()
{
using (var streamContent = new StreamContent(Request.Body))
{
//TODO check for token presence and reject if issue
var response = await _httpClient.PostAsync(string.Empty, streamContent);
var content = await response.Content.ReadAsStringAsync();
Response.StatusCode = (int)response.StatusCode;
Response.ContentType = response.Content.Headers.ContentType?.ToString();
Response.ContentLength = response.Content.Headers.ContentLength;
await Response.WriteAsync(content);
}
}
_httpClient being a HttpClient class instantiated somewhere else and being a singleton and with a BaseAddressof http://someexternalapp.com/api/
Also, is there a simpler approach for the token creation / token check than doing it manually?

If anyone is interested, I took the Microsoft.AspNetCore.Proxy code and made it a little better with middleware.
Check it out here: https://github.com/twitchax/AspNetCore.Proxy. NuGet here: https://www.nuget.org/packages/AspNetCore.Proxy/. Microsoft archived the other one mentioned in this post, and I plan on responding to any issues on this project.
Basically, it makes reverse proxying another web server a lot easier by allowing you to use attributes on methods that take a route with args and compute the proxied address.
[ProxyRoute("api/searchgoogle/{query}")]
public static Task<string> SearchGoogleProxy(string query)
{
// Get the proxied address.
return Task.FromResult($"https://www.google.com/search?q={query}");
}

I ended up implementing a proxy middleware inspired by a project in Asp.Net's GitHub.
It basically implements a middleware that reads the request received, creates a copy from it and sends it back to a configured service, reads the response from the service and sends it back to the caller.

This post talks about writing a simple HTTP proxy logic in C# or ASP.NET Core. And allowing your project to proxy the request to any other URL. It is not about deploying a proxy server for your ASP.NET Core project.
Add the following code anywhere of your project.
public static HttpRequestMessage CreateProxyHttpRequest(this HttpContext context, Uri uri)
{
var request = context.Request;
var requestMessage = new HttpRequestMessage();
var requestMethod = request.Method;
if (!HttpMethods.IsGet(requestMethod) &&
!HttpMethods.IsHead(requestMethod) &&
!HttpMethods.IsDelete(requestMethod) &&
!HttpMethods.IsTrace(requestMethod))
{
var streamContent = new StreamContent(request.Body);
requestMessage.Content = streamContent;
}
// Copy the request headers
foreach (var header in request.Headers)
{
if (!requestMessage.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray()) && requestMessage.Content != null)
{
requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray());
}
}
requestMessage.Headers.Host = uri.Authority;
requestMessage.RequestUri = uri;
requestMessage.Method = new HttpMethod(request.Method);
return requestMessage;
}
This method covert user sends HttpContext.Request to a reusable HttpRequestMessage. So you can send this message to the target server.
After your target server response, you need to copy the responded HttpResponseMessage to the HttpContext.Response so the user's browser just gets it.
public static async Task CopyProxyHttpResponse(this HttpContext context, HttpResponseMessage responseMessage)
{
if (responseMessage == null)
{
throw new ArgumentNullException(nameof(responseMessage));
}
var response = context.Response;
response.StatusCode = (int)responseMessage.StatusCode;
foreach (var header in responseMessage.Headers)
{
response.Headers[header.Key] = header.Value.ToArray();
}
foreach (var header in responseMessage.Content.Headers)
{
response.Headers[header.Key] = header.Value.ToArray();
}
// SendAsync removes chunking from the response. This removes the header so it doesn't expect a chunked response.
response.Headers.Remove("transfer-encoding");
using (var responseStream = await responseMessage.Content.ReadAsStreamAsync())
{
await responseStream.CopyToAsync(response.Body, _streamCopyBufferSize, context.RequestAborted);
}
}
And now the preparation is complete. Back to our controller:
private readonly HttpClient _client;
public YourController()
{
_client = new HttpClient(new HttpClientHandler()
{
AllowAutoRedirect = false
});
}
public async Task<IActionResult> Rewrite()
{
var request = HttpContext.CreateProxyHttpRequest(new Uri("https://www.google.com"));
var response = await _client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, HttpContext.RequestAborted);
await HttpContext.CopyProxyHttpResponse(response);
return new EmptyResult();
}
And try to access it. It will be proxied to google.com

A nice reverse proxy middleware implementation can also be found here: https://auth0.com/blog/building-a-reverse-proxy-in-dot-net-core/
Note that I replaced this line here
requestMessage.Content?.Headers.TryAddWithoutValidation(header.Key, header.Value.ToArray());
with
requestMessage.Headers.TryAddWithoutValidation(header.Key, header.Value.ToString());
Original headers (e.g. like an authorization header with a bearer token) would not be added without my modification in my case.

I had luck using twitchax's AspNetCore.Proxy NuGet package, but could not get it to work using the ProxyRoute method shown in twitchax's answer. (Could have easily been a mistake on my end.)
Instead I defined the mapping in Statup.cs Configure() method similar to the code below.
app.UseProxy("api/someexternalapp-proxy/{arg1}", async (args) =>
{
string url = "https://someexternalapp.com/" + args["arg1"];
return await Task.FromResult<string>(url);
});

Piggy-backing on James Lawruk's answer https://stackoverflow.com/a/54149906/6596451 to get the twitchax Proxy attribute to work, I was also getting a 404 error until I specified the full route in the ProxyRoute attribute. I had my static route in a separate controller and the relative path from Controller's route was not working.
This worked:
public class ProxyController : Controller
{
[ProxyRoute("api/Proxy/{name}")]
public static Task<string> Get(string name)
{
return Task.FromResult($"http://www.google.com/");
}
}
This does not:
[Route("api/[controller]")]
public class ProxyController : Controller
{
[ProxyRoute("{name}")]
public static Task<string> Get(string name)
{
return Task.FromResult($"http://www.google.com/");
}
}
Hope this helps someone!

Twitchax's answer seems to be the best solution at the moment. In researching this, I found that Microsoft is developing a more robust solution that fits the exact problem the OP was trying to solve.
Repo: https://github.com/microsoft/reverse-proxy
Article for Preview 1 (they actually just released prev 2): https://devblogs.microsoft.com/dotnet/introducing-yarp-preview-1/
From the Article...
YARP is a project to create a reverse proxy server. It started when we noticed a pattern of questions from internal teams at Microsoft who were either building a reverse proxy for their service or had been asking about APIs and technology for building one, so we decided to get them all together to work on a common solution, which has become YARP.
YARP is a reverse proxy toolkit for building fast proxy servers in .NET using the infrastructure from ASP.NET and .NET. The key differentiator for YARP is that it is being designed to be easily customized and tweaked to match the specific needs of each deployment scenario. YARP plugs into the ASP.NET pipeline for handling incoming requests, and then has its own sub-pipeline for performing the steps to proxy the requests to backend servers. Customers can add additional modules, or replace stock modules as needed.
...
YARP works with either .NET Core 3.1 or .NET 5 preview 4 (or later). Download the preview 4 (or greater) of .NET 5 SDK from https://dotnet.microsoft.com/download/dotnet/5.0
More specifically, one of their sample apps implements authentication (as for the OP's original intent)
https://github.com/microsoft/reverse-proxy/blob/master/samples/ReverseProxy.Auth.Sample/Startup.cs

Here is a basic implementation of Proxy library for ASP.NET Core:
This does not implement the authorization but could be useful to someone looking for a simple reverse proxy with ASP.NET Core. We only use this for development stages.
using System;
using System.Globalization;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Primitives;
namespace Sample.Proxy
{
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddLogging(options =>
{
options.AddDebug();
options.AddConsole(console =>
{
console.IncludeScopes = true;
});
});
services.AddProxy(options =>
{
options.MessageHandler = new HttpClientHandler
{
AllowAutoRedirect = false,
UseCookies = true
};
options.PrepareRequest = (originalRequest, message) =>
{
var host = GetHeaderValue(originalRequest, "X-Forwarded-Host") ?? originalRequest.Host.Host;
var port = GetHeaderValue(originalRequest, "X-Forwarded-Port") ?? originalRequest.Host.Port.Value.ToString(CultureInfo.InvariantCulture);
var prefix = GetHeaderValue(originalRequest, "X-Forwarded-Prefix") ?? originalRequest.PathBase;
message.Headers.Add("X-Forwarded-Host", host);
if (!string.IsNullOrWhiteSpace(port)) message.Headers.Add("X-Forwarded-Port", port);
if (!string.IsNullOrWhiteSpace(prefix)) message.Headers.Add("X-Forwarded-Prefix", prefix);
return Task.FromResult(0);
};
});
}
private static string GetHeaderValue(HttpRequest request, string headerName)
{
return request.Headers.TryGetValue(headerName, out StringValues list) ? list.FirstOrDefault() : null;
}
public void Configure(IApplicationBuilder app)
{
app.UseWebSockets()
.Map("/api", api => api.RunProxy(new Uri("http://localhost:8833")))
.Map("/image", api => api.RunProxy(new Uri("http://localhost:8844")))
.Map("/admin", api => api.RunProxy(new Uri("http://localhost:8822")))
.RunProxy(new Uri("http://localhost:8811"));
}
public static void Main(string[] args)
{
var host = new WebHostBuilder()
.UseKestrel()
.UseIISIntegration()
.UseStartup<Startup>()
.Build();
host.Run();
}
}
}

How to migrate Microsoft.OneDriveSDK v1 to v2?

I have a Xamarin based application which uses the Microsoft.OneDriveSDK nuget Package with version 1.x In this application I manage the OAuth stuff using Xamarin.Auth and thus get the access_token from that framework.
With the OneDriveSDK 1.x, I could provide this access token by redefining a few classes and then never had the API trying to fetch the token.
Now I wanted to migrate to version 2 and noticed that the previous classes got replaced and the API now uses Microsoft.Graph nuget package instead. So I had to implement the interface IAuthenticationProvider and did it like this:
public async Task AuthenticateRequestAsync(HttpRequestMessage request)
{
if (!string.IsNullOrEmpty(MicrosoftLiveOAuthProvider.Instance.AccessToken))
{
request.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("bearer", MicrosoftLiveOAuthProvider.Instance.AccessToken);
}
}
The code is called and properly provides the authentication token to the request headers. But once the SDK tries to use the token, I get an exception:
Exception of type 'Microsoft.Graph.ServiceException' was thrown.
Code: InvalidAuthenticationToken
Message: CompactToken parsing failed with error code: -2147184118
Now using google for this message always said the token is not JWT compliant and the SDK would then use it as microsoft live account token. But if this is the case, I wonder why it fails with V2 but works with V1.
Authentication is done against:
https://login.live.com/oauth20_authorize.srf
Any help is very mich appreciated!

I use a subclassed Xamarin.Auth WebRedirectAuthenticator with Microsoft.OneDriveSDK v2.0.0.
I get the initial access_token via that Xamarin.Auth subclass using a authorizeUrl: that is built via:
string GetAuthorizeUrl()
{
var requestUriStringBuilder = new StringBuilder();
requestUriStringBuilder.Append(Consts.MicrosoftAccountAuthenticationServiceUrl);
requestUriStringBuilder.AppendFormat("?{0}={1}", Consts.RedirectUriKeyName, Consts.Redirect_URI);
requestUriStringBuilder.AppendFormat("&{0}={1}", Consts.ClientIdKeyName, Consts.Client_ID);
requestUriStringBuilder.AppendFormat("&{0}={1}", Consts.ResponseTypeKeyName, Consts.TokenKeyName);
requestUriStringBuilder.AppendFormat("&{0}={1}", Consts.ScopeKeyName, Consts.Drive_Scopes);
return Uri.EscapeUriString(requestUriStringBuilder.ToString());
}
Once I have the access and refresh tokens, I can implement the IHttpProvider that needs passed to the OneDriveClient constructor in order to set access token in the http header:
public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request)
{
SetupHttpClient();
return _httpClient.SendAsync(request);
}
public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationToken cancellationToken)
{
SetupHttpClient();
return _httpClient.SendAsync(request, completionOption, cancellationToken);
}
HttpClient _httpClient;
void SetupHttpClient()
{
if (_httpClient == null)
{
_httpClient = new HttpClient();
var accessToken = _account.Properties["access_token"];
_httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
}
}
Create your OneDriveClient client using your IAuthenticationProvider and IHttpProvider objects (I just implement them on the same class that I am building all the OneDrive API calls), and every OnDrive request will use the access token from your saved Account.
Note: My IAuthenticationProvider implementation of AuthenticateRequestAsync currently does nothing, but you could do your Account setup here for a cleaner code flow.
var oneDriveClient = new OneDriveClient("https://api.onedrive.com/v1.0", this, this);
var pictureFolderItem = await oneDriveClient.Drive.Root.ItemWithPath("Pictures").Request().GetAsync();
Console.WriteLine(pictureFolderItem.Folder);
Refreshing is almost as easy, I store when the access token will expire (minus 5 minutes) and setup a timer to refresh it and re-save it to the Account. Do the same thing on app launch, if the user has an Account available and thus previously logged in, check if it is expired, refresh it, setup the background timer...
async Task<bool> GetRefreshToken(Account account)
{
// https://github.com/OneDrive/onedrive-api-docs/blob/master/auth/msa_oauth.md#step-3-get-a-new-access-token-or-refresh-token
OneDriveOAuth2Authenticator auth = OAuth2Authenticator();
var token = account.Properties["refresh_token"];
var expiresIn = await auth.RequestRefreshTokenAsync(token);
ResetRefreshTokenTimer(expiresIn);
return true;
}

Mobile Service Client throws exception when response is not found

I am trying to port an application from an azure mobile service to an azure web app. (the mobile service was working). I have added microsoft account authentication to the web-app, and the web app api has a MobileAppController attribute. I have a Universal windows app front end that calls the api. The app first checks if a player is in the database, if not I get a not found response. If I call the method using the following code with the MobileServiceClient I get an exception.
private async Task<HttpResponseMessage> GetAZMAsyncP(string apiext, IDictionary<string,string> param )
{
string myuri = String.Format("{0}{1}", urlbase, apiext);
//client is the MobileServiceClient that is correctly logged in
//I do not get response which is 404 not found, I get an exception "The request could not be completed, Not Found"
var response = await client.InvokeApiAsync(myuri, System.Net.Http.HttpMethod.Get, param);
return response;
}
If I call the api from an httpclient and add my own headers, which the mobile client is supposed to do for me, then I get the response as requested. Here is the code:
private async static Task<HttpResponseMessage> GetAZAsync(string apiext)
{
string completeUrl = String.Format("{0}{1}", urlbase, apiext);
// Call out to AZ
using (var http = new HttpClient())
{
// http.BaseAddress = new Uri(completeUrl);
HttpRequestMessage rq = new HttpRequestMessage()
{
RequestUri = new Uri(completeUrl),
Method = HttpMethod.Get
};
addauthheader(rq);
var response = await http.SendAsync(rq);
return response;
}
}
private static void addauthheader(HttpRequestMessage rq)
{
MobileServiceUser user = App.client.CurrentUser;
rq.Headers.Add("X-ZUMO-FEATURES", "AT,QS");
rq.Headers.Add("X-ZUMO-INSTALLATION-ID",
"ff90f37e-0c03-4c52-a343-af711752e383");
rq.Headers.Add("X-ZUMO-AUTH", user.MobileServiceAuthenticationToken);
rq.Headers.Add("Accept", "application/json");
rq.Headers.Add("User-Agent", "ZUMO/2.1");
rq.Headers.Add("User-Agent",
"(lang = Managed; os = Windows Store; os_version = --; arch = X86; version = 2.1.40707.0)");
rq.Headers.Add("X-ZUMO-VERSION",
"ZUMO/2.1(lang = Managed; os = Windows Store; os_version = --; arch = X86; version = 2.1.40707.0)");
rq.Headers.Add("ZUMO-API-VERSION", "2.0.0");
}
You can try this out as it is live (and buggy).
https://gamenote2.azurewebsites.net/api/Players?displayname=Paul Goldschmidt&teamid=arizona-diamondbacks
Should give you a 404,
https://gamenote2.azurewebsites.net/api/Players?displayname=Chase Utley&teamid=los-angeles-dodgers
should give you a chase utley object. (YOu will be asked to log into a Microsoft Account).
So my questions: 1. Can I fix the mobileclient call to get a response instead of an execption
2. Is there any good reason for me to be spending so much time on this.

If you examine the exception, you will note that the status code is in there - it's just in a property that is not serialized. Just surround your InvokeApiAsync() call with a try/catch and test for the StatusCode. It should be a lot easier than writing your own HTTP Client code for the same purpose.
Specifically, MobileServiceInvalidOperationException contains the HttpResponse of the failed request, so you can check exception.Response.StatusCode value.

WebException on HTTP request while debugging

I have a ASP.NET project which involves sending HTTP requests via the Web-API Framework. The following exception is only raised when debugging:
The server committed a protocol violation. Section=ResponseStatusLine
The project runs perfectly if I "Start Without Debugging".
How should I resolve this exception?
Any help is appreciated!
Update
The problem seems related to the ASP.NET MVC Identity Framework.
To access other Web-API methods, the client application has to first POST a login request (The login request does not need to be secure yet, and so I am sending the username and password strings directly to the Web-API POST method). If I comment out the login request, no more exception is raised.
Below are the relevant code snippets:
The Post method:
UserManager<ApplicationUser> UserManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext()));
AccountAccess ac = new AccountAccess();
public async Task<HttpResponseMessage> Post()
{
string result = await Request.Content.ReadAsStringAsync();
LoginMessage msg = JsonConvert.DeserializeObject<LoginMessage>(result);
HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
var user = UserManager.Find(msg.username, msg.password);
if (user == null)
return response;
if (user.Roles == null)
return response;
var role = from r in user.Roles where (r.RoleId == "1" || r.RoleId == "2") select r;
if (role.Count() == 0)
{
return response;
}
bool task = await ac.LoginAsync(msg.username, msg.password);
response.Content = new StringContent(task.ToString());
return response;
}
The Account Access class (simulating the default AccountController in MVC template):
public class AccountAccess
{
public static bool success = false;
public AccountAccess()
: this(new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext())))
{
}
public AccountAccess(UserManager<ApplicationUser> userManager)
{
UserManager = userManager;
}
public UserManager<ApplicationUser> UserManager { get; private set; }
public async Task<bool> LoginAsync(string username, string password)
{
var user = await UserManager.FindAsync(username, password);
if (user != null)
{
await SignInAsync(user, isPersistent: false);
return true;
}
else
{
return false;
}
}
~AccountAccess()
{
if (UserManager != null)
{
UserManager.Dispose();
UserManager = null;
}
}
private IAuthenticationManager AuthenticationManager
{
get
{
return HttpContext.Current.GetOwinContext().Authentication;
}
}
private async Task SignInAsync(ApplicationUser user, bool isPersistent)
{
AuthenticationManager.SignOut(DefaultAuthenticationTypes.ExternalCookie);
var identity = await UserManager.CreateIdentityAsync(user, DefaultAuthenticationTypes.ApplicationCookie);
AuthenticationManager.SignIn(new AuthenticationProperties() { IsPersistent = isPersistent }, identity);
}
}
Below are the relevant code snippets:
In client application:
public static async Task<List<T>> getItemAsync<T>(string urlAction)
{
message = new HttpRequestMessage();
message.Method = HttpMethod.Get;
message.RequestUri = new Uri(urlBase + urlAction);
HttpResponseMessage response = await client.SendAsync(message);
string result = await response.Content.ReadAsStringAsync();
List<T> msgs = JsonConvert.DeserializeObject<List<T>>(result);
return msgs;
}
In Web-API controller:
public HttpResponseMessage Get(string id)
{
HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
if (id == "ItemA")
{
List<ItemAMessage> msgs = new List<ItemAMessage>();
// some code...
response.Content = new StringContent(JsonConvert.SerializeObject(msgs));
}
else if (id == "ItemB")
{
List<ItemBMessage> msgs = new List<ItemBMessage>();
// some code...
response.Content = new StringContent(JsonConvert.SerializeObject(msgs));
}
return response;
}
Some observations I have:
I thought that I may need to send the request asynchronously (with the async-await syntax), but the exception still persists that way.
If I step through the code, the request does enter the HTTP method, but the code breaks at random line (Why?!) before returning the response, so I assume no response is being sent back.
I have tried the following solutions, as suggested in answers to similar questions, none of which works for me:
Setting useUnsafeHeaderParsing to true
Adding the header Keep-Alive: false
Changing the port setting of Skype (I don't have Skype, and port 80 and 443 are not occupied)
Additional information, in case they matter:
Mac OS running Windows 8.1 with VMware Fusion
Visual Studio 2013
.NET Framework 4.5
IIS Express Server
Update 2
The exception is resolved, but I am unsure of which modification did the trick. AFAIK, either one or both of the following fixed it:
I have a checkConnection() method, which basically sends a GET request and return true on success. I added await to the HttpClient.SendAsync() method and enforced async all the way up.
I retracted all code in the MainWindow constructor, except for the InitializeComponent() method, into the Window Initialized event handler.
Any idea?
Below are relevant code to the modifications illustrated above:
the checkConnectionAsync method:
public static async Task<bool> checkConnectionAsync()
{
message = new HttpRequestMessage();
message.Method = HttpMethod.Get;
message.RequestUri = new Uri(urlBase);
try
{
HttpResponseMessage response = await client.SendAsync(message);
return (response.IsSuccessStatusCode);
}
catch (AggregateException)
{
return false;
}
}
Window Initialized event handler (retracted from the MainWindow constructor):
private async void Window_Initialized(object sender, EventArgs e)
{
if (await checkConnectionAsync())
{
await loggingIn();
getItemA();
getItemB();
}
else
{
logMsg.Content = "Connection Lost. Restart GUI and try again.";
}
}
Update 3
Although this may be a little off-topic, I'd like to add a side note in case anyone else falls into this – I have been using the wrong authentication approach for Web-API to start with. The Web-API project template already has a built-in Identity framework, and I somehow "replaced" it with a rather simple yet broken approach...
This video is a nice tutorial to start with.
This article provides a more comprehensive explanation.

In the Client Application you are not awaiting task. Accessing Result without awaiting may cause unpredictable errors. If it only fails during Debug mode, I can't say for sure, but it certainly isn't the same program (extra checks added, optimizations generally not enabled). Regardless of when Debugging is active, if you have a code error, you should fix that and it should work in either modes.
So either make that function async and call the task with the await modifier, or call task.WaitAndUnwrapException() on the task so it will block synchronously until the result is returned from the server.

Make sure URL has ID query string with value either as Item A or Item B. Otherwise, you will be returning no content with Http status code 200 which could lead to protocol violation.

When you use SendAsync, you are required to provide all relevant message headers yourself, including message.Headers.Authorization = new AuthenticationHeaderValue("Basic", token); for example.
You might want to use GetAsync instead (and call a specific get method on the server).
Also, are you sure the exception is resolved? If you have some high level async method that returns a Task and not void, that exception might be silently ignored.