EF Core Loading Related Data

EmployeesController.cs

using AdvancedEFCore.Models;
using AdvancedEFCore.ViewModels;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Distributed;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace AdvancedEFCore.Controllers
{
    public class EmployeesController : Controller
    {
        private readonly MyApplicationContext _context;
        private readonly IDistributedCache _distributedCache;
        private readonly ILogger<EmployeesController> _logger;

        public EmployeesController(MyApplicationContext context, IDistributedCache distributedCache, ILogger<EmployeesController> logger)
        {
            _context = context;
            _distributedCache = distributedCache;
            _logger = logger;
        }

        [HttpGet]
        public IActionResult Index()
        {
            //Lazy Loading
            var employees = _context.Employees.ToList();
            return View(employees);
        }

        [HttpGet]
        public IActionResult Create()
        {
            ViewBag.Departments = GetDepartments();
            ViewBag.Skills = GetSkills();
            return View();
        }

        [HttpPost]
        public IActionResult Create(EmployeesViewModel viewModel)
        {
            if (ModelState.IsValid)
            {
                Employee employe = new Employee();
                employe.FirstName = viewModel.FirstName;
                employe.LastName = viewModel.LastName;
                employe.JoinedDate = viewModel.JoinedDate;
                employe.Salary = viewModel.Salary;
                employe.DepId = viewModel.DepartmentId;

                EmployeeProfile profile = new()
                {
                    Email = viewModel.Profile.Email,
                    Phone = viewModel.Profile.Phone,
                    EmployeeId = employe.Id
                };

                employe.Profile = profile;

                foreach (var skillId in viewModel.SkillIds)
                {
                    var skill = _context.Skills.Where(x => x.Id == skillId).FirstOrDefault();
                    employe.Skills.Add(skill);
                }

                _context.Employees.Add(employe);
                _context.SaveChanges();

                _distributedCache.Remove("Employees");

                return RedirectToAction("Index");
            }

            ViewBag.Departments = GetDepartments();
            ViewBag.Skills = GetSkills();

            return View(viewModel);
        }

        [HttpGet]
        public IActionResult Edit(int id)
        {
            var employee = _context.Employees
                                   .Include(x => x.Profile)
                                   .Include(x => x.Department)
                                   .Include(x => x.Skills)
                                   .FirstOrDefault(x => x.Id == id);

            EmployeesViewModel viewModel = new EmployeesViewModel();
            viewModel.FirstName = employee.FirstName;
            viewModel.LastName = employee.LastName;
            viewModel.Salary = employee.Salary;
            viewModel.JoinedDate = employee.JoinedDate;
            viewModel.DepartmentId = employee.DepId;
            viewModel.Profile = employee.Profile;
            viewModel.Version = employee.Version;

            viewModel.SkillIds = employee.Skills.Select(x => x.Id).ToArray();

            ViewBag.Departments = GetDepartments();
            ViewBag.Skills = GetSkills();

            return View(viewModel);
        }

        [HttpPost]
        public IActionResult Edit(EmployeesViewModel viewModel)
        {
            if (ModelState.IsValid)
            {
                var employee = _context.Employees
                                   .Include(x => x.Profile)
                                   .Include(x => x.Department)
                                   .Include(x => x.Skills)
                                   .FirstOrDefault(x => x.Id == viewModel.Id);

                employee.FirstName = viewModel.FirstName;
                employee.LastName = viewModel.LastName;
                employee.JoinedDate = viewModel.JoinedDate;
                employee.DepId = viewModel.DepartmentId;
                employee.Salary = viewModel.Salary;
                employee.Profile.EmployeeId = employee.Id;
                employee.Profile.Phone = viewModel.Profile.Phone;
                employee.Profile.Email = viewModel.Profile.Email;

                employee.Skills.Clear();

                foreach (var skillId in viewModel.SkillIds)
                {
                    var skill = _context.Skills.Where(x => x.Id == skillId).FirstOrDefault();
                    employee.Skills.Add(skill);
                }

                _context.Employees.Update(employee);
                _context.SaveChanges();

                return RedirectToAction("Index");
            }

            return View(viewModel);
        }

        [HttpGet]
        public IActionResult Delete(int id)
        {
            var employee = _context.Employees.FirstOrDefault(x => x.Id == id);
            return View(employee);
        }

        [HttpPost]
        [ActionName("Delete")]
        public IActionResult DeletePost(int id)
        {
            var employee = _context.Employees.FirstOrDefault(x => x.Id == id);
            _context.Employees.Remove(employee);
            _context.SaveChanges();

            return RedirectToAction("Index");
        }

        private List<SelectListItem> GetSkills()
        {
            var skills = _context.Skills.ToList();

            var dropDown = new List<SelectListItem>();

            foreach (var skill in skills)
            {
                dropDown.Add(new SelectListItem { Value = skill.Id.ToString(), Text = skill.Title });
            }

            return dropDown;
        }

        //List<SelectListItem>
        private List<SelectListItem> GetDepartments()
        {
            var departments = _context.Departments.ToList();

            var dropDown = new List<SelectListItem>();

            foreach (var department in departments)
            {
                dropDown.Add(new SelectListItem { Value = department.Id.ToString(), Text = department.Name });
            }

            return dropDown;
        }

        [HttpGet]
        public IActionResult IndexEager()
        {
            var cachedEmpsJson = _distributedCache.GetString("Employees");

            var jsonOptions = new JsonSerializerOptions();
            jsonOptions.ReferenceHandler = ReferenceHandler.Preserve;
            jsonOptions.WriteIndented = true;

            if (cachedEmpsJson == null)
            {
                _logger.LogInformation("Cached Missed");
                var employees = _context.Employees
                                    .Include(x => x.Profile)
                                    .Include(x => x.Department)
                                    .Include(x => x.Skills)
                                    .AsSingleQuery()
                                    .AsNoTracking()
                                    .ToList();

                var empsJson = JsonSerializer.Serialize(employees, jsonOptions);
                _distributedCache.SetString("Employees", empsJson);

                return View(employees);
            }

            _logger.LogInformation("Reading from Cache");
            var cachedEmployees = JsonSerializer.Deserialize<List<Employee>>(cachedEmpsJson, jsonOptions);
            return View(cachedEmployees);
        }

        [HttpGet]
        public IActionResult IndexExplicit()
        {
            var employees = _context.Employees.ToList();

            foreach (var employee in employees)
            {
                _context.Entry(employee).Collection(x => x.Skills).Load();
                _context.Entry(employee).Reference(x => x.Department).Load();
                _context.Entry(employee).Reference(x => x.Profile).Load();
            }

            return View(employees);
        }
    }
}