在我得到这个代码之前：
Department.cs:

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

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

在DepartmentController中添加动作方法：

//GET
        public IActionResult Add()
        {
            return View();
        }

        //POST
        [HttpPost]
        [ValidateAntiForgeryToken]
        public IActionResult Add(Department obj)
        {
            if (_appDbContext.Departments.Where(x => x.Name.Contains(obj.Name)).Any())
            {
                ModelState.AddModelError("Name", "Department name already exists");
            }

            if (ModelState.IsValid)
            {
                _appDbContext.Departments.Add(obj);
                _appDbContext.SaveChanges();
                TempData["success"] = "Department created successfully";

                return RedirectToAction("Index");
            }
            return View(obj);
        }

Add.cshtml:

@model Department

<form method="post">
    <div class="border p-3 mt-4">
        <div class="row pb-2">
            <h2 class="text-primary">Add Department</h2>
            <hr />
        </div>
        @*<div asp-validation-summary="All"></div>*@
        <div class="mb-3">
            <label asp-for="Name" class="mb-1"></label>
            <input asp-for="Name" class="form-control" />
            <span asp-validation-for="Name" class="text-danger"></span>
        </div>
        <button type="submit" class="btn btn-primary" style="width:150px">Add</button>
        <a asp-controller="Department" asp-action="Index" class="btn btn-secondary" style="width:150px">
            Back to List
        </a>
    </div>
</form>

@section Scripts{
    @{
        <partial name="_ValidationScriptsPartial" />
    }
}

上面的代码在添加记录时运行良好，但在Department.cs类发生以下变化后（删除数据库并重新更新以确保重新开始），它就不再运行了：

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

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

        public ICollection<Equipment> Equipments{ get; set; }
    }

我不确定是否应该在控制器或视图中添加新属性，以及具体要添加什么。