从ViewModel检索数据

我现在有两个模型和一个ViewModel。下面列出了它们。我想在索引方法上显示员工模型中的所有字段以及部门模型中的2个字段。因此，我创建了带有所有字段的ViewModel，并在我的Create Method上添加了一个用于检索数据的public IEnumerable<SelectListItem> DeptList { get; set; }到DropDownList（效果很好）。

员工模式：

    public class Employee
{
    [Key]
    public int EmpId { get; set; }
    [Column(TypeName = "varchar(50)")]
    [MaxLength(50)]
    [Required(ErrorMessage = "First Name is Required")]    
    public string EmpFirstName { get; set; }
    [Column(TypeName = "varchar(50)")]
    [MaxLength(50)]
    [Required(ErrorMessage = "Last Name is required")]
    public string EmpLastName { get; set; }
    [Column(TypeName = "varchar(10)")]
    [DataType(DataType.PhoneNumber)]
    [MaxLength(10)]
    [Required(ErrorMessage = "Phone Number is required")]
    public string EmpPhoneNumber { get; set; }
    [Column(TypeName = "datetime2(7)")]
    [DataType(DataType.Date)]
    [Required(ErrorMessage = "Start Date is required")]
    [DisplayFormat(DataFormatString = "{0:D}")]
    public DateTime EmpStartDate { get; set; }
    public int DeptId { get; set; }
    public Department Department { get; set; }
}

部门模型：

    public class Department
{
    [Key]
    public int DeptId { get; set; }
    [Required(ErrorMessage = "Department Name is required")]
    [Column(TypeName = "varchar(50)")]
    [MaxLength(50)]
    public string DeptName { get; set; }
    public List<Employee> Employees { get; set; }
}

EmployeeViewModel：

如果可能的话，我只想为我的CRUD创建一个ViewModel。

    public class EmployeeViewModel
{
    public int EmpId { get; set; }
    public string EmpFirstName { get; set; }
    public string EmpLastName { get; set; }
    public string EmpPhoneNumber { get; set; }
    public DateTime EmpStartDate { get; set; }
    public int DeptId { get; set; }
    public string DeptName { get; set; }
    public IEnumerable<SelectListItem> DeptList { get; set; }
}

员工管理员：

    public class EmployeeController : Controller
{
    private DataEntryContext _context;
    public EmployeeController(DataEntryContext context)
    {
        _context = context;
    }
    // GET: /<controller>/
    public IActionResult Index()
    {
        return View(_context.Employees.ToList());
    }
    // Retrieve List of Departments
    private IEnumerable<SelectListItem> GetDeptList()
    {
        var dept = _context.Departments
            .Select(s => new SelectListItem
            {
                Value = s.DeptId.ToString(),
                Text = s.DeptName
            })
            .ToList();
        return (dept);
    }
    public IActionResult Create()
    {
        EmployeeViewModel selectList = new EmployeeViewModel();
        selectList.DeptList = GetDeptList();
        return View(selectList);
    }
    [HttpPost]
    [ValidateAntiForgeryToken]
    public IActionResult Create(EmployeeViewModel employee)
    {
        if (ModelState.IsValid)
        {
            var emp = new Employee();
            {
                emp.EmpFirstName = employee.EmpFirstName;
                emp.EmpLastName = employee.EmpLastName;
                emp.EmpPhoneNumber = employee.EmpPhoneNumber;
                emp.EmpStartDate = employee.EmpStartDate;
                emp.DeptId = employee.DeptId;
            }
            _context.Employees.Add(emp);
            _context.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(employee);
    }
}

查看索引方法：

我在这个视图的顶部添加了@model IEnumerable<DataEntryMVC.Models.EmployeeViewModel>。

@foreach (var item in Model)
{
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.EmpFirstName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.EmpLastName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.EmpPhoneNumber)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.EmpStartDate)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.DeptName)
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id = item.EmpId })
        </td>
    </tr>
}

检索数据时收到的错误消息：

处理请求时发生未处理的异常。

InvalidOperationException：传递到ViewDataDictionary的模型项的类型为System.Collections.Generic.List`1[DataEntryMVC.Models.Employee]，但此ViewDataDiction实例需要类型为"System.Collections.Generic.IEnumerable`1[DDataEntryMVC.Models.EmpireeViewModel]"的模型项。

此外，我是否正确处理了将数据添加到数据库的创建方法？

public IActionResult Index()
{
    var list=_context.Employees
                     .Select(s=> new EmployeeViewModel { 
                                                         EmpId =s.EmpId ,
                                                         EmpFirstName=s.EmpFirstName,
                                                         EmpLastName=s.EmpLastName,
                                                         EmpPhoneNumber=s.EmpPhoneNumber,
                                                         EmpStartDate=s.EmpStartDate,
                                                         DeptName=s.Department.DeptName
                                                       }).ToList();
    return View(list);
}