HttpContext NULL issue?? System.NullReferenceException on HttpContextAccessor? Core 2.1

[codeinflash]

Describe the bug

I am using asp.net core 2.1

Because HttpContext becomes null, I get System.NullReferenceException.
I have interface called 'IUserRepository' and it is implemented in Startup class.
Startup.cs:

public void ConfigureServices(IServiceCollection services) {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

			services.AddSession(options => {
                options.IdleTimeout = TimeSpan.FromHours(12);
            });
            services.AddHttpContextAccessor(); //core 2.1
            services.AddTransient<IUserRepository, UserRepository>();
        }

Then I get user's info and tells whether the user is validated user or not.
However, I get System.NullReferenceException: Object reference not set to an instance of an object.
at Services.UserRepository.GetUserNetworkId() in ...\Services\UserRepository.cs:line 122
I marked where is the line#122 in below code.
UserRepository.cs:

public class UserRepository : IUserRepository
    {
        private readonly IHttpContextAccessor _httpContextAccessor;

        public UserRepository(IHttpContextAccessor httpContextAccessor)
        {
            _httpContextAccessor = httpContextAccessor;
        }

        public string GetUserNetworkId()
        {
            string userName = null;
            string NetworkId = null;

            //-------------checking where fails
            if (_httpContextAccessor == null)
            {
                throw new Exception("In IsUserValidated() - Error: _httpContextAccessor == null");
            }

            if (_httpContextAccessor.HttpContext == null)
            {
                throw new Exception("In IsUserValidated() - Error: _httpContextAccessor.HttpContext == null");
            }

            if (_httpContextAccessor.HttpContext.User == null)
            {
                throw new Exception("In IsUserValidated() - Error: _httpContextAccessor.HttpContext.User == null");
            }

            if (_httpContextAccessor.HttpContext.User.Identity == null)
            {
                throw new Exception("In IsUserValidated() - Error: _httpContextAccessor.HttpContext.User.Identity == null");
            }
            //-------------checking where fails done

            var identity = _httpContextAccessor.HttpContext.User.Identity;

            if (identity.IsAuthenticated)
            {
                userName = identity.Name;
            }
            else
            {
                **** line#122 **** var basicCredentials = new BasicAuthenticationHeader(_httpContextAccessor.HttpContext);
                userName = basicCredentials.UserName;
            }

            if (Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Development"
                && Environment.GetEnvironmentVariable("USER_NETWORK_ID") != null) // used for testing in development by setting overriding environmental varibles
            {
                NetworkId = Environment.GetEnvironmentVariable("USER_NETWORK_ID");
            }
            else
            { // assume production
                NetworkId = userName.Split("\\").Last();
            }

            return NetworkId;
        }

        public int GetUserPhoneKey()
        {
            var userInfo = UserInfo.GetUserInfo(GetUserNetworkId());
            int PhoneKey = userInfo.userPhoneKeyId;
            return PhoneKey;
        }
    }

The line#122 creates a class BasicAuthenticationHeader
and decodes AuthenticationHeader of the HttpConext.

I think (guess) there is where the HttpContext becomes Null out.
class BasicAuthenticationHeader.cs:
private readonly string _authenticationHeaderValue;

        private string[] _splitDecodedCredentials;

        public bool IsValidBasicAuthenticationHeaderValue { get; private set; }
        public string UserName { get; private set; }

		public BasicAuthenticationHeader(HttpContext context)
        {
			var basicAuthenticationHeader = context.Request.Headers["Authorization"]
				.FirstOrDefault(header => header.StartsWith("Basic", StringComparison.OrdinalIgnoreCase));

			if (!string.IsNullOrWhiteSpace(basicAuthenticationHeader))
            {
                _authenticationHeaderValue = basicAuthenticationHeader;
                if (TryDecodeHeaderValue())
                {
                    ReadAuthenticationHeaderValue();
                }
            }
        }

The more weird is that it happens at random, and I don't know why HttpContext gets lost.

Please help.

Thank you.

To Reproduce

Steps to reproduce the behavior:

1. Using this version of ASP.NET Core '2.1'

[Tratcher]

Realize that IHttpContextAccessor is a feature of last resort as it's easy to use incorrectly. Where does GetUserNetworkId get called from in your application? HttpContext is only valid during a request, and it should only be accessed on the main request thread.

[codeinflash]

I have 6 controllers that implements IUserRepository like below HomeController and calls the function GetUserNetworkId()
ex) HomeController.cs:

public class HomeController : Controller
	{
        private readonly IUserRepository _userRepository;

        public HomeController(IUserRepository userRepository)
        {
            _userRepository = userRepository;
        }
	public IActionResult Index()
	{
            var userValidated = _userRepository.IsUserValidated();
            if (!userValidated)
            { ViewData["Error"] = "Please be sure you are NOT logging in with your email address. You need to use your network id.The id(" + _userRepository.GetUserNetworkId() + ") you provided was not found in the Phone Directory. Please contact the Service Desk";
            }
	    return View("vHome");
	}
}

[Tratcher]

HttpContext is available in HomeController, pass it directly into GetUserNetworkId rather than relying on IHttpContextAccessor.

[poke]

Or if you just want to use the ClaimsPrincipal, then just pass User to the user repository.

[codeinflash]

Is passing HttpContext to a different controller or interface safe do so??

[Tratcher]

You can pass it anywhere you like so long as only one thread is using it at a time and they stop using it after the end of the request.

[Eilon]

Before the end of the request 😄

[blowdart]

As this appears to be a misunderstanding of how long a context lasts for, and advice has been given, closing

[codeinflash]

@blowdart Can I ask how long does Http Context last????

[Eilon]

It lasts for the duration of the request, and can be used only from the request thread.