How to add related data in Entity Framework? What should be passed as parameters? I have the following code which doesn't work.

Model classes:

public class Department
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [DisplayName("Department Name")]
        public string Name { get; set; }
    }

public class Equipment
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [DisplayName("Equipment Name")]
        public string Name { get; set; }

        [Required]
        public int Amount { get; set; }

        [Required]
        public string Status { get; set; }
        public int DepartmentId { get; set; }
        public Department Department { get; set; }

    }

Create Action Method in EquipmentController.cs:

        // GET: Equipment/Create
        public IActionResult Create()
        {
            ViewData["DepartmentId"] = new SelectList(_context.Departments, "Id", "Name");
            return View();
        }

        // POST: Equipment/Create
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Create([Bind("Id,Name,Amount,Status,DepartmentId")] Equipment equipment)
        {
            if (ModelState.IsValid)
            {
                _context.Add(equipment);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            ViewData["DepartmentId"] = new SelectList(_context.Departments, "Id", "Name", equipment.DepartmentId);
            return View(equipment);
        }

View:

@model Equipment

@{
    ViewData["Title"] = "Create";
}

<h1>Create</h1>

<h4>Equipment</h4>
<hr />
<div >
    <div >
        <form asp-action="Create">
            <div asp-validation-summary="ModelOnly" ></div>
            <div >
                <label asp-for="Name" ></label>
                <input asp-for="Name"  />
                <span asp-validation-for="Name" ></span>
            </div>
            <div >
                <label asp-for="Amount" ></label>
                <input asp-for="Amount"  />
                <span asp-validation-for="Amount" ></span>
            </div>
            <div >
                <label asp-for="Status" ></label>
                <input asp-for="Status"  />
                <span asp-validation-for="Status" ></span>
            </div>
            <div >
                <label asp-for="DepartmentId" ></label>
                <select asp-for="DepartmentId" class ="form-control" asp-items="ViewBag.DepartmentId"></select>
            </div>
            <div >
                <input type="submit" value="Create"  />
            </div>
        </form>
    </div>
</div>

<div>
    <a asp-action="Index">Back to List</a>
</div>

The data being passed in the debugger:

When I click the Create button the data won't be saved into the database. I want to be able to add equipments with a DepartmentId linked to them and also being to print out equipments with their department names.

CodePudding user response：

I know what you mean, could you try the below model to create a new project?

Department:

  public class Department
    {
    [Key]
    public int Id { get; set; }

    [Required]
    [DisplayName("Department Name")]
    public string Name { get; set; }
    public ICollection<Equipment>? Equipment { get; set; }
    }

Equipment

 public class Equipment
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [DisplayName("Equipment Name")]
        public string Name { get; set; }

        [Required]
        public int Amount { get; set; }

        [Required]
        public string Status { get; set; }
        [ForeignKey("DepartmentId")]
        public int DepartmentId { get; set; }
        public Department Department { get; set; }

    }

In asp.net core6 remove below line from the project.csproj:

 <Nullable>enable</Nullable>

result: