Hi all am trying to get employee tree Hierarchy in drop down

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C#

ASP.NET

C# sharp code which i have tried is below

public void GetReportee()
{
    IList<Employee> lstEmployee = new List<Employee>();
    IList<Employee> ListOne = new List<Employee>();

    lstEmployee = objBCHReviewService.GetReportee(out ListOne);
     IList<Employee> listEmployeeTwo = new List<Employee>();
     int   count=1;
    ddlEmployee.Items.Insert(0, new ListItem("All", "0"));
    foreach (Employee emp in ListOne)
    {
        ddlEmployee.Items.Add(emp.FirstName);
        ddlEmployee.Items[count].Attributes.Add("style", "color:blue");
        listEmployeeTwo = lstEmployee.Where(x => x.ManagerEmployeeId == emp.EmployeeId).ToList();
        foreach (Employee em in listEmployeeTwo)
        {
            String EmpName = "&nbsp;&nbsp;&nbsp;" + em.FirstName;
            ddlEmployee.Items.Add(new ListItem(Server.HtmlDecode(EmpName), Convert.ToString(em.EmployeeId)));
        }
        count += listEmployeeTwo.Count() + 1;
    }

}

        public IList<employee> GetReportee(out IList<employee>ListOne)
        {
            IList<employee> objListOneEmployee = new List<employee>();
            IList<employee> objListEmployee = new List<employee>();

            Employee objEmployee = null;
            using (DbCommand dbcGetEmployee = db.GetStoredProcCommand("usp_GetEmployees"))
            {
                db.AddInParameter(dbcGetEmployee, "@EmployeeUID", DbType.String, "512677");
                IDataReader dr = db.ExecuteReader(dbcGetEmployee);
               while (dr.Read())
               {
                   objEmployee = new Employee();
                   if (dr["EmployeeId"] != DBNull.Value)
                       objEmployee.EmployeeId = Convert.ToInt16(dr["EmployeeId"]);
                   if (dr["FirstName"] != DBNull.Value)
                       objEmployee.FirstName = Convert.ToString(dr["FirstName"]);
                   if (dr["LastName"] != DBNull.Value)
                       objEmployee.LastName = Convert.ToString(dr["LastName"]);
                   objListOneEmployee.Add(objEmployee);
               }
                ListOne=objListOneEmployee;
               dr.NextResult();
                while(dr.Read())
                {
                    objEmployee = new Employee();
                    if (dr["EmployeeId"] != DBNull.Value)
                        objEmployee.EmployeeId = Convert.ToInt16(dr["EmployeeId"]);
                    if (dr["FirstName"] != DBNull.Value)
                        objEmployee.FirstName = Convert.ToString(dr["FirstName"]);
                    if (dr["ManagerEmployeeId"] != DBNull.Value)
                        objEmployee.ManagerEmployeeId = Convert.ToInt16(dr["ManagerEmployeeId"]);
                    if (dr["ManagerName"] != DBNull.Value)
                        objEmployee.ManagerName = Convert.ToString(dr["ManagerName"]);
                    objListEmployee.Add(objEmployee);
                }
                
                 
            }
            return objListEmployee;
        }

Please help me I want to get like this in my drop down.if am logging in the drop down it should contain names who all are having my EmployeeID as their SupervisorID

1)User1--( User1 supervisor id will be My EmployeeId)
    1.1)user2--(user2's supervisor id will be  User1's EmployeeId )
        1.1.1)user3--(user3's supervisor id will be  User2's EmployeeId )
        1.1.2)user4--(user4's supervisor id will be  User2's EmployeeId )
              1.1.2.1)user5--(user5's supervisor id will be  User4's EmployeeId )
                     1.1.2.1.1)--(user6's supervisor id will be  User5's EmployeeId) 
2)user7--( User1 supervisor id will be My EmployeeId)

        2.1)user8--(user8's supervisor id will be  User7's EmployeeId )
            2.1.1)user9--(user3's supervisor id will be  User8's EmployeeId )
            2.1.2)user10--(user4's supervisor id will be  User8's EmployeeId )
3)user11--( User1 supervisor id will be My EmployeeId)