Self Reference ASP.NET

Question

Guys I am implementing a very basic web application that has ONE Class Only (Employee), however this class should have a Manager(who is also an employee) and they should have one-to-many relationship (1 or Many Employees should have :1 Manager Only, 1 Manager could have more the 1 Employee).

I missed up implementing the Model , the DbContext and the View and now the system is not running and here is what I have done so far:

1. The Model:

public class Employee

    {

        [Key]

        [DisplayName("Employee ID")]

        public int EmployeeID { get; set; }

        [DisplayName("Last Name")]

        [Required]

        public string LastName { get; set; }

        [DisplayName("First Name")]

        [Required]

        public string FirstName { get; set; }

        public int? ManagerID { get; set; }

        public Employee Manager { get; set; }

        public ICollection<Employee> ListOfEmployees { get; set; }

    }

2. DbContext:

public class ApplicationDbContext:DbContext

    {

        public ApplicationDbContext(DbContextOptions<ApplicationDbContext>options):base(options)

        {

        }

        public DbSet<Employee> Employees { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Employee>()

                .HasOne(manager => manager.Manager)

                .WithMany(emp => emp.ListOfEmployees)

                .HasForeignKey(m => m.ManagerID);

            base.OnModelCreating(modelBuilder);

        }

    }

3. The View (Should be a drop down list where you only show the employees related to a manager that you choose from a drop down list):

@model IEnumerable<Employee>

@{

    ViewData["Title"] = "Employee List";

}

<label for="Manager">Choose a Manager:</label>

    <select name="Manager" id="MangerID">

        

        @foreach(var obj in Model)

        {

            

            <option value=@obj.ManagerID>@obj.LastName</option>

            

        }

       

    </select>

4. Controller:

//Home Page

        public IActionResult Index()

        {

            var DataSource=_db.Employees.Select(emp => new

            {

                LastName = emp.LastName,

                ManagerName = emp.Manager == null ? "Super Boss" : emp.Manager.LastName

            }).ToList();

            

            return View(DataSource);

        }

Answer 1

I have an example for this done in a console project which will work in an ASP.NET Core project found here.