System.ArgumentNullException:Value cannot be null. Parameter name:userManager

Question

Screenshot I am getting an error to IdentityConfig.cs file and will show below which line, but when i add that return object within the method with a watch when debugging, i am getting the name 'Value cannot be null, parameter name:userManager. What could be the possibility of this errors? Kindly please assist me and thanks.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.EntityFramework;
using Microsoft.AspNet.Identity.Owin;
using Microsoft.Owin;
using Microsoft.Owin.Security;
using System.Net.Mail;
using System.Net;
using System.Web.Configuration;
using eNtsaTrainingRegistration.Models;

namespace eNtsaTrainingRegistration
{
    public class EmailService : IIdentityMessageService
    {
        public Task SendAsync(IdentityMessage message)
        {
            var mailMessage = new MailMessage();
            mailMessage.To.Add(new MailAddress(message.Destination));
            mailMessage.From = new MailAddress("Gcobani Mkontwana <ggcobani@gmail.com>");
            mailMessage.Subject = message.Subject;
            mailMessage.IsBodyHtml = true;
            mailMessage.Body = message.Body;

            using (var smtp = new SmtpClient())
            {
                var credential = new NetworkCredential
                {
                    UserName = WebConfigurationManager.AppSettings["UserName"],
                    Password = Helper_b.Decrypt(WebConfigurationManager.AppSettings["UserPassword"])
                };
                smtp.Credentials = credential;
                smtp.Host = WebConfigurationManager.AppSettings["SMTPName"];
                smtp.Port = int.Parse(WebConfigurationManager.AppSettings["SMTPPort"]);
                smtp.EnableSsl = true;
                smtp.Send(mailMessage);
            }
            return Task.FromResult(0);
        }
    }

    public class SmsService : IIdentityMessageService
    {
        public Task SendAsync(IdentityMessage message)
        {
            return Task.FromResult(0);
        }
    }
    // add another method here.
    public class ApplicationUserManager : UserManager<ApplicationUser>
    {
        public ApplicationUserManager(IUserStore<ApplicationUser> store)
            : base(store)
        {
        }

        public static ApplicationUserManager Create(IdentityFactoryOptions<ApplicationUserManager> options, IOwinContext context)
        {
            var manager = new ApplicationUserManager(new UserStore<ApplicationUser>(context.Get<ApplicationDbContext>()));
            // Configure validation logic for usernames
            manager.UserValidator = new UserValidator<ApplicationUser>(manager)
            {
                AllowOnlyAlphanumericUserNames = false,
                RequireUniqueEmail = true
            };

            // Configure validation logic for passwords
            manager.PasswordValidator = new PasswordValidator
            {
                RequiredLength = 6,
                RequireNonLetterOrDigit = true,
                RequireDigit = true,
                RequireLowercase = true,
                RequireUppercase = true,
            };

            // Configure user lockout defaults
            manager.UserLockoutEnabledByDefault = true;
            manager.DefaultAccountLockoutTimeSpan = TimeSpan.FromMinutes(5);
            manager.MaxFailedAccessAttemptsBeforeLockout = 5;

            // Register two factor authentication providers. This application uses Phone and Emails as a step of receiving a code for verifying the user
            // You can write your own provider and plug it in here.
            manager.RegisterTwoFactorProvider("Phone Code", new PhoneNumberTokenProvider<ApplicationUser>
            {
                MessageFormat = "Your security code is {0}"
            });
            manager.RegisterTwoFactorProvider("Email Code", new EmailTokenProvider<ApplicationUser>
            {
                Subject = "Security Code",
                BodyFormat = "Your security code is {0}"
            });
            manager.EmailService = new EmailService();
            manager.SmsService = new SmsService();
            var dataProtectionProvider = options.DataProtectionProvider;
            if (dataProtectionProvider != null)
            {
                manager.UserTokenProvider =
                    new DataProtectorTokenProvider<ApplicationUser>(dataProtectionProvider.Create("ASP.NET Identity"));
            }
            return manager;
        }


    }
    // Configure the application sign-in manager which is used in this application.
    public class ApplicationSignInManager : SignInManager<ApplicationUser, string>
    {
        public ApplicationSignInManager(ApplicationUserManager userManager, IAuthenticationManager authenticationManager)
            : base(userManager, authenticationManager) // Error UserManager is null
        {
        }

        public override Task<ClaimsIdentity> CreateUserIdentityAsync(ApplicationUser user)
        {
            return user.GenerateUserIdentityAsync((ApplicationUserManager)UserManager);
        }

        public static ApplicationSignInManager Create(IdentityFactoryOptions<ApplicationSignInManager> options, IOwinContext context)
        {
            return new ApplicationSignInManager(context.GetUserManager<ApplicationUserManager>(), context.Authentication); // error CS103, the name 'GetUserManager does not exist in current context.
        }
    }
    public class ApplicationRoleManager:RoleManager<IdentityRole>
    {
        public ApplicationRoleManager(IRoleStore<IdentityRole, string> roleStore)
            :base(roleStore)
        {

        }
        public static ApplicationRoleManager Create(IdentityFactoryOptions<ApplicationRoleManager> options, IOwinContext context)
        {
            var appRoleManager = new ApplicationRoleManager(new RoleStore<IdentityRole>(context.Get<ApplicationDbContext>()));

            return appRoleManager;
        }
    }
}

Answer 1

In your Startup.Auth.cs have you configured the following?:

app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);
app.CreatePerOwinContext<ApplicationRoleManager>(ApplicationRoleManager.Create);