generic repository in asp.net core code example

Example: generic repository pattern c#

// IGenericRepository.cs :
namespace RepositoryUsingEFinMVC.GenericRepository
{
    public interface IGenericRepository<T> where T : class
    {
        IEnumerable<T> GetAll();
        T GetById(object id);
        void Insert(T obj);
        void Update(T obj);
        void Delete(object id);
        void Save();
    }
}

// GenericRepository.cs :
namespace RepositoryUsingEFinMVC.GenericRepository
{
    public class GenericRepository<T> : IGenericRepository<T> where T : class
    {
        private EmployeeDBContext _context = null;
        private DbSet<T> table = null;
        public GenericRepository()
        {
            this._context = new EmployeeDBContext();
            table = _context.Set<T>();
        }
        public GenericRepository(EmployeeDBContext _context)
        {
            this._context = _context;
            table = _context.Set<T>();
        }
        public IEnumerable<T> GetAll()
        {
            return table.ToList();
        }
        public T GetById(object id)
        {
            return table.Find(id);
        }
        public void Insert(T obj)
        {
            table.Add(obj);
        }
        public void Update(T obj)
        {
            table.Attach(obj);
            _context.Entry(obj).State = EntityState.Modified;
        }
        public void Delete(object id)
        {
            T existing = table.Find(id);
            table.Remove(existing);
        }
        public void Save()
        {
            _context.SaveChanges();
        }
    }
}
// Main:
using System.Web.Mvc;
using RepositoryUsingEFinMVC.DAL;
using RepositoryUsingEFinMVC.GenericRepository;
namespace RepositoryUsingEFinMVC.Controllers
{
    public class EmployeeController : Controller
    {
        private IGenericRepository<Employee> repository = null;
        public EmployeeController()
        {
            this.repository = new GenericRepository<Employee>();
        }
        public EmployeeController(IGenericRepository<Employee> repository)
        {
            this.repository = repository;
        }
        [HttpGet]
        public ActionResult Index()
        {
            var model = repository.GetAll();
            return View(model);
        }
        [HttpGet]
        public ActionResult AddEmployee()
        {
            return View();
        }
        [HttpPost]
        public ActionResult AddEmployee(Employee model)
        {
            if (ModelState.IsValid)
            {
                repository.Insert(model);
                repository.Save();
                return RedirectToAction("Index", "Employee");
            }
            return View();
        }
        [HttpGet]
        public ActionResult EditEmployee(int EmployeeId)
        {
            Employee model = repository.GetById(EmployeeId);
            return View(model);
        }
        [HttpPost]
        public ActionResult EditEmployee(Employee model)
        {
            if (ModelState.IsValid)
            {
                repository.Update(model);
                repository.Save();
                return RedirectToAction("Index", "Employee");
            }
            else
            {
                return View(model);
            }
        }
        [HttpGet]
        public ActionResult DeleteEmployee(int EmployeeId)
        {
            Employee model = repository.GetById(EmployeeId);
            return View(model);
        }
        [HttpPost]
        public ActionResult Delete(int EmployeeID)
        {
            repository.Delete(EmployeeID);
            repository.Save();
            return RedirectToAction("Index", "Employee");
        }
    }
}