ASP.NET Core MVC frontend development List show View keep getting System.Collections.Generic.List

Question

I'm trying to display data from three models, have two models(STAFF、DEPARTMENT) using show data, make Cascading Dropdown one model(STAFF_PERMISSION) insert data,make

but keep getting: The model item passed into the ViewDataDictionary is of type 'System.Collections.Generic.List1[Voyager.Models.Department.Staff_To_Show]

StaffPermission.cshtml

@model Voyager.Models.Department.Staff_To_Show
    
    @{
        ViewBag.Title = "new";
        
    }
    
    <h2>new</h2>
    
    <form  method="post" action="/Home/StaffPermission">
    
        @Html.AntiForgeryToken()
      
        <div class="form-horizontal">
    
       <select id="DepartmentNumber" name="DepartmentNumber"class="form-control">
                <option value="">select</option>
    
                  @foreach (var item in Model.Departments)
        {
               
            <option value="@item.DepartmentNumber"> @Html.DisplayFor(modelItem => item.DepartmentNumber)</option>
    
        }
               
            </select>
    <br/>
       <select id="DepartmentNumber" name="DepartmentNumber"class="form-control">
                <option value="">select</option>
    
                  @foreach (var item in Model.Staffs)
        {
               
            <option value="@item.StaffNumber"> @Html.DisplayFor(modelItem => item.StaffNumber)</option>
    
        }
               
            </select>
            
            <hr />
                  <div class="form-group">
                @Html.LabelFor(model => model.StaffPermissions, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.StaffPermissions, new { htmlAttributes = new { @class = "form-control" } })
                    @Html.ValidationMessageFor(model => model.StaffPermissions, "", new { @class = "text-danger" })
                </div>
            </div>
    
     
    
            <div class="form-group">
                <div class="col-md-offset-2 col-md-10">
                    <input type="submit" value="add" class="btn btn-success" />
                </div>
            </div>
        </div>
      </form>

HomeController.cs

 [HttpGet("[action]")]
    public ActionResult StaffPermission()
    {
        var query = dbContext.staff.ToList();
        var queryDepartment = dbContext.Departments.ToList();

        var model = new List<Staff_To_Show>();

        List<Department> dataDepartment = new List<Department>();
        dataDepartment.AddRange(queryDepartment);

        List<staff> datastaff = new List<staff>();
        datastaff.AddRange(query);

        model.Add(new Staff_To_Show() { Departments = dataDepartment });
        model.Add(new Staff_To_Show() { Staffs = datastaff });


        return View(model);
    }

    [HttpPost]
    public ActionResult StaffPermission(String DepartmentNumber, String StaffNumber, string AesUpd)
    {

        if (string.IsNullOrWhiteSpace(DepartmentNumber))
        {
            ModelState.AddModelError("Department", "error");
            return View();
        }
        else
        {

            string[] password = getTool.Create(AesUpd);

            StaffPermission addstaff = new StaffPermission();

            addstaff.AesUpd = password[0];
            addstaff.AesKey = password[1];
            addstaff.AesIv = password[2];
            addstaff.LastChangePasswordTime = DateTime.Now;
            addstaff.CreateDate = DateTime.Now;
            addstaff.LastUpd = password[0];
            addstaff.LastKey = password[1];
            addstaff.LastIv = password[2];
            addstaff.IsEnabled = true;
            addstaff.StaffNumber = StaffNumber;
            addstaff.DepartmentNumber = Convert.ToInt16(DepartmentNumber);

            dbContext.StaffPermissions.Add(addstaff);
            dbContext.SaveChanges();

            return View();

        }

    }

StaffToShow.cs

    public partial class Staff_To_Show
    {

        public List<Department> Departments { get; set; } = null!;
        public List<staff> Staffs { get; set; } = null!;
        public StaffPermission StaffPermissions { get; set; } = null!;
    }

StaffPermission.cs

using System;
using System.Collections.Generic;

namespace Voyager.Models.Department
{
    public partial class StaffPermission
    {
        public int DepartmentNumber { get; set; }
        public string StaffNumber { get; set; } = null!;
        public string AesUpd { get; set; } = null!;
        public string AesKey { get; set; } = null!;
        public string AesIv { get; set; } = null!;
        public DateTime? CreateDate { get; set; }
        public string? LastUpd { get; set; }
        public string? LastKey { get; set; }
        public string? LastIv { get; set; }
        public DateTime? LastChangePasswordTime { get; set; }
        public bool? IsEnabled { get; set; }
        public virtual staff StaffNumberNavigation { get; set; } = null!;
    }
}

staff.cs

 public partial class staff
    {
        public int DepartmentNumber { get; set; }
        public string StaffNumber { get; set; } = null!;
        public string? Name { get; set; }
        public string? Phone { get; set; }
        public string? Address { get; set; }
        public string? Email { get; set; }
        public bool? IsEnabled { get; set; }
        public DateTime RecDate { get; set; }

        public virtual Department DepartmentNumberNavigation { get; set; } = null!;
        public virtual StaffPermission StaffPermission { get; set; } = null!;
    }

Department.cs

    public partial class Department
    {
        public Department()
        {
            staff = new HashSet<staff>();
        }

        public int DepartmentNumber { get; set; }
        public string? DepartmentName { get; set; }

        public virtual ICollection<staff> staff { get; set; }
    }

Any help would be appreciated

Answer 1

Your view expects a model of type Staff_To_Show but in your HttpGet Method StaffPermission you create and pass a model of type List<Staff_To_Show>. So your method should look like this:

[HttpGet("[action]")]
public ActionResult StaffPermission()
{
    var datastaff = dbContext.staff.ToList();
    var dataDepartment = dbContext.Departments.ToList();

    var model = new Staff_To_Show {
        Departments = dataDepartment,
        Staffs = datastaff
    };

    return View(model);
}

I also removed the redundant list creation code since department and staff are already lists.