Argument 1: cannot convert from 'System.Collections.Generic.List' to 'System.Collections.Generic.List'

Question

I'm learning Asp.net Core and building a simple web with CRUD operations, SQL server and using Entity Framework. When I try to build a sorting method I git this error in this line at parameter employees

return View(this.SortEmployees(employees, SortField, CurrentSortField, SortDirection));

and that's the error:

Severity    Code    Description Project File    Line    Suppression State
Error   CS1503  Argument 1: cannot convert from 'System.Collections.Generic.List<EmployeesApp.Models.Employee>' to 'System.Collections.Generic.List<EmployeesApp.Controllers.Employee>' EmployeesApp    

that's my Model:

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace EmployeesApp.Models
{
    [Table("Employee", Schema ="dbo")]

    public class Employee
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        [Display(Name ="Employee ID")]
        public int EmployeeId { get; set; }


        [Required]
        [Column(TypeName ="varchar(5)")]
        [MaxLength(5)]
        [Display(Name ="Employee Number")]
        public string EmployeeNumber { get; set; }


        [Required]
        [Column(TypeName = "varchar(150)")]
        [MaxLength(100)]
        [Display(Name = "Employee Name")]
        public string EmployeeName { get; set; }


        [Required]
        [DataType(DataType.Date)]
        [Display(Name ="Date of Birth")]
        [DisplayFormat(DataFormatString = "{0:dd-MMM-yyyy}")]
        public DateTime DOB { get; set; }


        [Required]
        [DataType(DataType.Date)]
        [Display(Name = "Hiring Date")]
        [DisplayFormat(DataFormatString = "{0:dd-MMM-yyyy}")]
        public DateTime HiringDate { get; set; }


        [Required]
        [Column(TypeName ="decimal(12,2)")]
        [Display(Name ="Gross Salary")]
        public decimal GrossSalary { get; set; }


        [Required]
        [Column(TypeName = "decimal(12,2)")]
        [Display(Name = "Net Salary")]
        public decimal NetSalary { get; set; }


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



        [Display(Name = "Department")]
        [NotMapped]
        public string DepartmentName { get; set; }


        public virtual Department Department { get; set; }
    }
}

and that's my COntroller:

namespace EmployeesApp.Controllers

{

    public enum SortDirection
    {
        Ascending,
        Descending
    }


    public class Employee : Controller
    {
       
        HRDatabaseContext dbContext = new HRDatabaseContext();

        public IActionResult Index(string SortField, string CurrentSortField, SortDirection SortDirection)
        {
            var employees = GetEmployees();
            return View(this.SortEmployees(employees, SortField, CurrentSortField, SortDirection));
        }



        private List<Models.Employee> GetEmployees()
        {
            return (from Employee in dbContext.Employees
                    join Department in dbContext.Departments on Employee.DepartmentId equals Department.DepartmentId
                    select new Models.Employee
                    {
                        EmployeeId = Employee.EmployeeId,
                        EmployeeName = Employee.EmployeeName,
                        DOB = Employee.DOB,
                        HiringDate = Employee.HiringDate,
                        GrossSalary = Employee.GrossSalary,
                        NetSalary = Employee.NetSalary,
                        DepartmentId = Employee.DepartmentId,
                        DepartmentName = Department.DepartmentName

                    }).ToList();
        }


        public IActionResult Add()
        {
            ViewBag.Department = this.dbContext.Departments.ToList();
            return View();
        }


        [HttpPost]
        public IActionResult Add(Models.Employee model)
        {
            ModelState.Remove("EmployeeID");
            ModelState.Remove("Department");
            ModelState.Remove("DepartmentName");
            if (ModelState.IsValid)
            {
                dbContext.Employees.Add(model);
                dbContext.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.Department = dbContext.Departments.ToList();
            return View("Add", model);
        }


        public IActionResult Edit(int ID)
        {
            HRDatabaseContext dbContext1 = dbContext;
            Models.Employee data = dbContext1.Employees.Where(e => e.EmployeeId == ID).FirstOrDefault();
           

            ViewBag.Department = this.dbContext.Departments.ToList();
            return View("Add", data);
        }


        [HttpPost]
        public IActionResult Edit(Models.Employee model)
        {
            ModelState.Remove("EmployeeID");
            ModelState.Remove("Department");
            ModelState.Remove("DepartmentName");
            if (ModelState.IsValid)
            {
                dbContext.Employees.Update(model);
                dbContext.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.Department = dbContext.Departments.ToList();
            return View();
        }


        public IActionResult Delete(int ID)
        {
            Models.Employee data = this.dbContext.Employees.Where(e => e.EmployeeId == ID).FirstOrDefault();

            if (data != null)
            {
                dbContext.Employees.Remove(data);
                dbContext.SaveChanges();
            }

            return RedirectToAction("Index");
        }

     
        private List<Employee> SortEmployees(List<Employee> employees, String sortField, string currentSortField, SortDirection sortDirection)
        
        {
            if (string.IsNullOrEmpty(sortField))
            {
                
                ViewBag.SortField = "EmployeeNumber";
                ViewBag.SortField = SortDirection.Ascending;

            }
            else
            {
                if (currentSortField == sortField)
                
                {
                    ViewBag.SortDirection = sortDirection == SortDirection.Ascending ? SortDirection.Descending : SortDirection.Ascending;
                    
                }
                else
                    ViewBag.SortDirection = sortDirection == SortDirection.Ascending;
                    ViewBag.SortField = sortField;

            }

            //* create the sorting proccess
            var propertyInfo = typeof(Employee).GetProperty(ViewBag.SortField);
            if (ViewBag.SortDirection == SortDirection.Ascending)
            {
                employees = employees.OrderBy(e => propertyInfo.GetValue(e, null)).ToList();
            }
            else
            {
                employees = employees.OrderByDescending(e => propertyInfo.GetValue(e, null)).ToList();

            }

            return employees;
        }
    }
}   

Answer 1

Your SortEmployees method in your controller takes a List<Employee> which in this context is a Controllers.Employee and not a Models.Employee as you suspect.

The best solution in this case is to rename your Controller to EmployeeController to follow the ASP.NET convention. In ASP.NET controllers are always named [Name]Controller.