问列表中的层次结构雇员/经理

EN

public class Employees
{
    public int empId{ get; set; }
    public string empName { get; set; }
    public Employees(int id, string name)
    {
        empId= id;
        empName = name;
    }
}
public class EmployeeManager
{
    public int empmgr_id { get; set; }
    public int emp_id { get; set; }
    public int mgr_id{ get; set; }
    public EmployeeManager(int emid, int eid, int mid)
    {
        empmgr_id = emid;
        emp_id = eid;
        mgr_id= mid;
    }
}

public static class EmpMgrData
{
    public static IEnumerable<Employees> EmpList()
    {
        var lstEmp = new List<Employees>();
        lstEmp .Add(new Employees(1,"Emp 1"));
        lstEmp .Add(new Employees(2,"Emp 2"));
        lstEmp .Add(new Employees(3,"Emp 3"));
        lstEmp .Add(new Employees(4,"Emp 4"));
        lstEmp .Add(new Employees(5,"Emp 5"));
        lstEmp .Add(new Employees(6,"Emp 6"));
        lstEmp .Add(new Employees(7,"Emp 7"));
        lstEmp .Add(new Employees(8,"Emp 8"));
        lstEmp .Add(new Employees(9,"Emp 9"));
        lstEmp .Add(new Employees(10,"Emp 10"));
        lstEmp .Add(new Employees(11,"Emp 11"));
        lstEmp .Add(new Employees(12,"Emp 12"));
        lstEmp .Add(new Employees(13,"Emp 13"));
        lstEmp .Add(new Employees(14,"Emp 14"));
        lstEmp .Add(new Employees(15,"Emp 15"));
        lstEmp .Add(new Employees(16,"Emp 16"));
        lstEmp .Add(new Employees(17,"Emp 17"));
        lstEmp .Add(new Employees(18,"Emp 18"));
        lstEmp .Add(new Employees(19,"Emp 19"));
        lstEmp .Add(new Employees(20,"Emp 20"));

        return lstEmp ;
    }

    public static IEnumerable<EmployeeManager> EmpMgrList()
    {
        var lstEmpMgr = new List<EmployeeManager>
                                   {
                                       new EmployeeManager(1,18,19),
                                       new EmployeeManager(2,17,20),
                                       new EmployeeManager(3,19,17),
                                       new EmployeeManager(4,14,15),
                                       new EmployeeManager(5,13,15),
                                       new EmployeeManager(6,12,13),
                                       new EmployeeManager(7,9,13),
                                       new EmployeeManager(8,10,13),
                                       new EmployeeManager(9,11,13),
                                       new EmployeeManager(10,6,5), 
                                       new EmployeeManager(11,7,5), 
                                       new EmployeeManager(12,8,5), 
                                       new EmployeeManager(13,5,4), 
                                       new EmployeeManager(14,4,20), 
                                       new EmployeeManager(15,2,4), 
                                       new EmployeeManager(16,1,3), 
                                       new EmployeeManager(17,3,20)
                                   };
        return lstEmpMgr ;
    }

}
private void Form1_Load(object sender, EventArgs e)
    {
        //Displaying list of persons in the combo box
        var empList = EmpMgrData.EmpList();
        comboBox1.DataSource = empList;
        comboBox1.DisplayMember = "empName";
        comboBox1.ValueMember = "empId";
    }

 private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(comboBox1.DisplayMember))
        {
            listBox1.DataSource = null;
            listBox1.Items.Clear();
            var personKey = ((Employees)comboBox1.SelectedItem).empId;
            var personname = ((Employees)comboBox1.SelectedItem).empName;
            List<EmployeeManager> hierarchyDownEmployees = null;
            List<Employees> hierarchyDownEmployeesName = null;
            hierarchyDownEmployees = EmpMgrData.EmpMgrList().ToList();
            //Using an Extension method to get the hierarchy of employees for the selected person.First we find all the direct employees of selected person and  using the extension method, we will find the hierarchy                   
            List<int> hEmployees = new List<int>(hierarchyDownEmployees.GetHierarchyEmployees(personKey));
            for (int i = 0; i < hEmployees.Count; i++)
            {
                hEmployees.AddRange(hierarchyDownEmployees.GetHierarchyEmployees(hEmployees[i]).Except(hEmployees));
            }
            //Finding the EmpName of the hierarchy employees
            hierarchyDownEmployeesName = EmpMgrData.EmpList().Where(n => hEmployees.Any(s => s == n.empId)).ToList();

            //Displaying the Hierarchy Employee Names of selected person to the list box
            if (hierarchyDownEmployeesName != null && hierarchyDownEmployeesName.Count() > 0)
            {
                label2.Text = "All Employees under " + comboBox1.Text + " are: " + string.Join(", ", hEmployees);
                listBox1.DataSource = hierarchyDownEmployeesName;
                listBox1.DisplayMember = "empName";
                listBox1.ValueMember = "empId";
                listBox1.SelectedIndex = -1;
            }                
        }
    }
}
public static class Hierarchy
{
    //Extension method to get the Employee Hierarchy of the selected person
    public static IEnumerable<int> GetHierarchyEmployees(this IEnumerable<EmployeeManager> employees, int empID)
    {
        return from emp in employees
               where emp.mgr_id == empID
               select emp.emp_id ;
    }
}