ASP-Zacodovka-Users

1) ---- Model -----

public class User
    {
        [Key]
        public int UserId { get; set; }

        [Column(TypeName = "nvarchar(100)")]
        public string Username { get; set; }

        [PassValidation(10)]
        [Column(TypeName = "nvarchar(100)")]
        public string Password { get; set; }


        [Display(Name = "Confirm password")]
        [NotMapped]
        public string ConfirmPassword { get; set; }

        [Column(TypeName = "int")]
        public int Age { get; set; }
    }


2) -- DB context --
 public class ApplicationDbContext : DbContext
    {
        public  ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
            : base(options)
        {
        }

        public DbSet<User> users { get; set; }
    }

3) -- appsettings.json -> Add connection string

 "ConnectionStrings": {
    "UserDbStr": "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=UsersDB;"
  }

4) --.... Startup.cs -> void Configure()...
            services.AddDbContext<ApplicationDbContext>(dbContOp => dbContOp.UseSqlServer(Configuration.GetConnectionString("UserDbStr")));

5) -- Package manager Console ---

Add-Migration "InitialCreate"
Update-Database

6) -- Scaffold


7) -- Custom validation
 public class PassValidation : ValidationAttribute
    {
        private readonly int _minL;

        public PassValidation(int minL)
        {
            this._minL = minL;
        }
        public override bool IsValid(object value)
        {
            if (value == null)
            {
                return false;
            }
            string pass = value as string;
            if (pass.Length < _minL)
            {
                return false;
            }
            return true;
        }
    }

8)  -- Add Session

8.1  ... public void ConfigureServices(IServiceCollection services)....
    services.AddSession(options => {
                options.IdleTimeout = TimeSpan.FromMinutes(60); //You can set Time
            });

8.2 ... public void Configure()...
app.UseSession();

9. -- Hash SHA256 --
 public class Crypto
    {
        public static string ComputeSha256Hash(string rawData)
        {
            // Create a SHA256
            using (SHA256 sha256Hash = SHA256.Create())
            {
                // ComputeHash - returns byte array
                byte[] bytes = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(rawData));

                // Convert byte array to a string
                StringBuilder builder = new StringBuilder();
                for (int i = 0; i < bytes.Length; i++)
                {
                    builder.Append(bytes[i].ToString("x2"));
                }
                return builder.ToString();
            }
        }
    }


10 --- Login Action ---
 public async Task<IActionResult> Login(string Uname, string Pass)
        {
            string hPass = Utilities.Crypto.ComputeSha256Hash(Pass);
            var user = await _context.users
                .FirstOrDefaultAsync(m => m.Username == Uname && m.Password == hPass);
            if (user == null)
            {
                ViewData["result"] = "Invalid username or password!";
                return View();
            }
            HttpContext.Session.Set("Username", Encoding.UTF8.GetBytes(user.Username));
            HttpContext.Session.Set("Age", Encoding.UTF8.GetBytes(user.Age.ToString()));
            return RedirectToAction("Index", "WebSystem");
        }

11.  Log to system
 public IActionResult Index()
        {
            byte[] buffer = new byte[100];
            bool hasuser = HttpContext.Session.TryGetValue("Username", out buffer);
            if (hasuser)
            {
                ViewData["user"] = Encoding.UTF8.GetString(buffer);
            }
            bool hasage = HttpContext.Session.TryGetValue("Age", out buffer);
            if(hasage)
            {
                ViewData["age"] = int.Parse(Encoding.UTF8.GetString(buffer));
            }
            else
            {
                ViewData["age"] = "---";
            }
            if (hasuser)
            {
                return View();
            }
            else
            {
                return RedirectToAction("Login", "Users");
            }
        }

12. --- Logout --
 public IActionResult Logout()
      {
            HttpContext.Session.Clear();
            return RedirectToAction("Login", "Users");
       }
 }