private void LoadComboBoxes()
{
    _empNames = _dapperHandler.EmployeesAsTable();
    AssignComboBox(cBRepFilter, _empNames);
    AssignComboBox(cBEmpName, _empNames);
}
        public IEnumerable<Employee> Employees()
        {
            _employees = null;
            using (var sqlConnection = new SqlConnection(_connectionString))
            {
                sqlConnection.Open();
                _employees = sqlConnection.Query<Employee>(Properties.Resources.selectEmployee);
                sqlConnection.Close();
            }
            return _employees;
        }
public List<Employee> UniqueEmployees()
        {
            if (_employees == null) Employees();
            var employees = _employees.ToList();
            var i = 0;
            var initalCount = employees.Count;
            while (i < initalCount)
            {
                var count = employees.Count(x => employees[i].EmpNum == x.EmpNum);
                if (count > 1)
                {
                    employees.Remove(employees[i]);
                    initalCount--;
                    continue;
                }
                i++;
            }
            return employees;
        }

        public DataTable EmployeesAsTable()
        {
            var tmp = To.DataTable(UniqueEmployees().OrderBy(x => x.EmpLastName).ToList());
            return tmp;
        }

        private void AssignComboBox(ComboBox comboBox, DataTable empNames)
        {
            // Assign ComboBox.DataSource
            comboBox.ValueMember = "EmpNum";
            comboBox.DisplayMember = "EmpFullName";
            comboBox.DataSource = empNames;
        }

    public class Employee
    {
        public int Id { get; set; }
        public string CardNum { get; set; }
        public string EmpFirstName { get; set; }
        public string EmpLastName { get; set; }
        public string EmpFullName => $"{EmpLastName}, {EmpFirstName}";
        public string EmpSupervisor { get; set; }
        public string EmpNum { get; set; }
    }