How do I resolve error 'cannot implicitly convert type 'string' to string[]

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I have a form whereby i need to do select multiple employees on a HtmlDropDownFor. I have used an SelectListItem and in my controller i am getting an exception 'Cannot implicitly convert type 'string' to string[] ' on the property pertaining to the employee i.e on line

request.EmployeeNumber = Convert.ToString(formcollection["EmployeeNumber"]);

I also have a related exception 'Cannot implicitly convert type 'string[]' to 'string'' on the function that loads an individual employee in the model i.e

This is how im getting the employees :

private static IEnumerable<SelectListItem> GetEmployees()
       {
           string department = string.Empty;
           department = System.Web.HttpContext.Current.Session["Department"].ToString();

           string number = string.Empty;
           number = System.Web.HttpContext.Current.Session["UserId"].ToString();

           List<SelectListItem> employees = new List<SelectListItem>();
           using (SqlConnection conn = new SqlConnection(Helpers.DatabaseConnect))
           {

               SqlCommand cmd = new SqlCommand("SELECT DisplayName,EmployeeNumber FROM Users WHERE Active=" + Convert.ToInt32(Helpers.parameters.active) + " AND Department=" + Convert.ToInt32(department) + "", conn);

               conn.Open();
               SqlDataReader dr = cmd.ExecuteReader();
               while (dr.Read())
               {
                   employees.Add(new SelectListItem
                   {
                       Text = dr["DisplayName"].ToString(),
                       Value = dr["EmployeeNumber"].ToString()
                   });
               }
               conn.Close();
           }

           return employees;
       }

In model OverTimeRequest.cs i have :

[Required]
        [Display(Name = "Employee ")]
        public string[] EmployeeNumber { get; set; }
        public Employee Employee { get; set; }
        public String DisplayName { get; set; }
		public IEnumerable<SelectListItem> employees { get; set; }

Controller :

[HttpPost]
       public ActionResult NewOverTimeRequest(FormCollection formcollection)
       {

           Models.Employee.OverTimeRequest request = new Models.Employee.OverTimeRequest();
           try
           {

               var batch = new OvertimeBatch();
               batch.AppliedBy = Convert.ToString(Session["UserId"]);
               batch.Justification = Convert.ToString(formcollection["Justification"]);
               batch.rate = Convert.ToInt32(formcollection["RateId"]);
               batch.NumberOfHour = Convert.ToInt32(formcollection["Hours"]);
               batch.Month = Convert.ToDateTime(formcollection["PayMonth"]);
               batch.AppliedOn = DateTime.Now;
               batch.id = batch.save();

               request.employees = GetEmployees();
               request.Rates = PopulateOverTimeRates();

               request.EmployeeNumber = Convert.ToString(formcollection["EmployeeNumber"]);
               request.RateId = Convert.ToInt32(formcollection["RateId"]);
               request.Justification = Convert.ToString(formcollection["Justification"]);
               request.Hours = Convert.ToInt32(formcollection["Hours"]);
               request.PayMonth = Convert.ToDateTime(formcollection["PayMonth"]);
               request.AppliedBy = Convert.ToString(Session["UserId"]);
               request.AppliedOn = DateTime.Now;

               DateTime Today = request.PayMonth;
               var startdate = new DateTime(Today.Year, Today.Month, 1);
               request.PayMonth = startdate.AddMonths(1).AddDays(-1);

               PayRunController payrun = new PayRunController();

               var employees = request.EmployeeNumber.Split(',');


               request.OverTimeAmount = 0.00;

               double total = 0.0;
               if (ModelState.IsValid)
               {
                   foreach (var employee in employees)
                   {
                      // request.OverTimeAmount = payrun.CalculateOverTimeAmount(employee, request.RateId);
                       total += request.OverTimeAmount;

                       using (SqlConnection conn = new SqlConnection(Helpers.DatabaseConnect))
                       {

                           SqlCommand cmd = new SqlCommand("SubmitOverTimeRequest", conn);
                           cmd.CommandType = CommandType.StoredProcedure;


                           cmd.Parameters.AddWithValue("@EmployeeNumber", employee);
                           cmd.Parameters.AddWithValue("@OverTimeRate", request.RateId);
                           cmd.Parameters.AddWithValue("@Justification", request.Justification);
                           cmd.Parameters.AddWithValue("@NumberOfHours", request.Hours);
                           cmd.Parameters.AddWithValue("@PayMonth", request.PayMonth);
                           cmd.Parameters.AddWithValue("@Amount", request.OverTimeAmount);
                           cmd.Parameters.AddWithValue("@AppliedBy", request.AppliedBy);
                           cmd.Parameters.AddWithValue("@AppliedOn", request.AppliedOn);
                           cmd.Parameters.AddWithValue("@OverTimeBatch", batch.id);

                           conn.Open();
                           cmd.ExecuteNonQuery();

                       }

                   }
                   batch.TotalAmount = total;
                   batch.updateTotalAmount();

                   return RedirectToAction("OverTime");
               }

           }

           catch (Exception ex)
           {
               ViewBag.ErrorMessage = ex.Message;
               return View(request);
           }

           return RedirectToAction("OverTime");
       }

This is how im getting the data in the view NewOverTimeRequest.cshtml :

@Html.DropDownListFor(m => m.EmployeeNumber, Model.employees, "Please Select", htmlAttributes: new { @class = "form-control" })
                                                               @Html.ValidationMessageFor(model => model.EmployeeName, "", new { @class = "text-danger" })

Anyone with ideas on how i can properly implement the functionality.

What I have tried:

I have searched sources and suggestions point to that i should use a range in GetEmployees function. Also i have tried using a forech in the view as below but its not working since the example im using does not use a select element, but rather HtmlDropDownFor/Html.ListBoxFor

m.EmployeeNumber, Model.employees, "Please Select", htmlAttributes: new { @class = "form-control" })
                                                               @Html.ValidationMessageFor(model => model.EmployeeName, "", new { @class = "text-danger" })>

I am following the answer from this thread asp.net mvc 3 - How do you properly create a MultiSelect <select> using the DropdownList helper? - Stack Overflow[^]